Carriers - design/usage tipps?

I always try to put on largest hull possible.

Usually put one set of armor on them (usually missiles for longest range). 

Then add all remaining space for more carrier modules (unless I need it to go a certain speed), but I usually use these to protect assets rather than hunt down things.

Late game I will use a Huge hull, with 1 transport module and build above as my  "Colony Warship" with lots of movement (usually 50-100 if not more). I then send packs of these out to take planets. 

I set my carriers to support... put no weapons or defenses on them... if I do... I put a missile weapon typically... but generally prefer any support module that affects the whole fleet, or more carrier modules.

Carriers then get paired with heavy defense laden ships with escort roles... and of course standard glass cannon attack ships with Capital role.

This ensures that the carriers will pretty much always die last. With no space wasted on defenses.

The last reply is the most efficient, but do remember to limit yourself on the number of strike craft you're bringing to fights.  You can only take so many carriers before you're hindering yourself.  After a point additional ships don't get you anywhere and you begin weakening the power of your fleet.

How so?

Obviously you need sufficient defense, but why not have all offense in carriers? I don't do so... but mostly out of habit.

There's a limit of 64 ships per side per engagement. Hull capacity spent on carrier modules beyond the number necessary to get [real ships in fleet] + [fighters in fleet] = 64 is, as a result, kind of wasted, though if I'm not mistaken the 'extra' fighters do allow the fleet to continue fielding an apparently-full fighter group despite losses for at least a little while.

Yes, if you have hundreds of fighters, you'll hit that limit, and blow the extra power from all that wasted space and get creamed.  The extra fighters most definitely did not join the battle the last time I played, perhaps that has changed recently, in which case this may not be true at all depending on how targeting is decided.

I meant for subsequent engagements. I.e. you send in your carrier fleet of 14 ships which has, say, 100 fighters, so up to 50 fighters in the engagement, and the carrier fleet loses 30 fighters in the engagement. Next engagement you have 70 fighters in the fleet, which means you still get 50 fighters at the start of the fight, which makes it appear as though the fleet is still at full strength. Not sure if it still works that way, but it used to.

I use all three types of hulls for my carriers, depending on the circumstances.

Cargo: I use these as "budget" carriers, for when I need to save on manufacturing costs or, more frequently, account for Logistics limitations. These usually have enough space for a Carrier Module or a High Capacity Carrier Module later on, but I could never figure out a way to stack a second module on them no matter how many capacity or miniaturization techs I take. So instead, I stack weapons on these with the remaining hull space. It's not because I expect them to contribute significantly to the battle - they have no defenses, so they're SOL if anything gets the chance to take a potshot at them - but the weapons are there on the off-chance that if enemy Interceptors close in to engage on my fleet's screening Guardians, the Cargo Carriers can lay down supporting firepower for the latter. This makes them more like aviation cruisers in the vein of the Kuznetsov-class; not great at either role, but better than nothing.

Large: I use hulls of this size as my standard carriers, because they have just enough space to fit two Carrier Modules. Or later on, one High Capacity and one standard Carrier Module. This makes for a respectable number of Assault Fighters, and a valuable element of my midgame fleets. Of course, it means that they don't have any more space left for anything more than the first tier of weapons; but hey, they're my dedicated carriers, that's perfectly fine by me.

Huge: Now we're getting into supercarrier territory. My homebrewed Nimitz design can carry up to 3 High Capacity modules, or even 4 with full hull capacity and miniaturization techs. That's enough firepower that, when I'm in a position to produce these in the late game, they generally phase out my soft-skinned Capitals as the primary offensive element of my fleets.

Some nice info here. I didn't know about the 64 ship limit.

FWIW I did try carriers based on cargo hulls in my last yor game, started with one module, and managed to cram in a second after researching/tech trading for capacity techs, still some had room for some defenses, engines etc. Those did well in combi with escorts and capitals.

Have any of you ever seen the AI use interceptors? As in the role? I haven't so I'm a little confused as to why you'd arm or armor a cargo carrier (support)...

I load them up with assist modules or sensors and one carrier module.

Doesn't hurt to have armed cargo carrier designs just in case, if and when Frogboy overhauls the ship combat portion to have the AI actually take advantage of the ship roles feature. Defenses are pointless since carriers are already SOL if it's their turn to take hits, but weapons might conceivably be useful now, or in the future.

Besides, it's not like Interceptors can actually carry out the role of hunting Supports like they're supposedly intended to, even if the AI used them. If this ship guide is still current, Interceptors would have to take out the opposing Guardians... and then double back to wipe the opposing Escorts before they can proceed to finish off the opposing Supports. That means Guardians are obsolete in their intended role of protecting Supports, since Escorts can do so just as well and better. Yeah, I think that's kind of stupid too, but that's the game for you, what can you do.

For me, the key to using Guardians is what their targeting priorities are if there are no enemy Interceptors around; Assault. That means while Capitals might be preoccupied battering down the enemy Capitals or Escorts, Guardians might actually have a use in clearing out the enemy carrier Assault Fighters.

That's why I designed a Huge Guardian carrying 4 Guardian Drone modules; it's the best idea I can think of for countering carrier fighter swarms, while avoiding the overkill issues that Large/Huge Capitals/Escorts suffer dealing with them. Of course, it's still just pure theorycrafting, I haven't actually had the opportunity to test it out in practice yet.