Add more AI players and there will be less colonization rush.  Change map settings to have less planets to rush to.  Why is it unbalanced?  Are you better than the AI at it, or are they better at it than you?  

What does "measured in weeks" have to do with game balance?  It is just an imaginary number to provide flavor to the turn count.

I have seen distance based large empire penalties.  I have very mixed feelings about that mechanic, especially when applied to oversized empires and maps.  For many of us, supporting over sized empires is why we bought the game in the first place.  

I like playing on Gifted, too.  I am not at war at the moment, but there is a Crusade coming.  

It's not a case of I'm better at it. I'm pretty much completely new to the game, but it's something that straight away seems out of place or unbalanced. I've got settings to occasional habitable planets and normal amount of civspace for huge size map.

my gripe is.. as a newly formed space empire without a shipyard. I go from that to pumping out 12 colonies, without anyone bothering them no matter how far or undefended they are. actually.I've built no warships at all. I did this as a reaction to seeing ai coming and settling on Mars  (rather than a planet near them). 

I assume the population is counted in the billions? so if I remove 0.5b people from earth.. this should be a fairly monumental task, more so than building factories on a undeveloped  home world.  and not one I should be able to repeat x12 4turns apart without any hazard to these colony ships. that's my angle. 

do I need to up the level. or will that just mean ai out rushes me?

it's similar to how in civ games it's annoying having to do a settler rush. they built some mechanics to slow that down.