Idea for 6S FLM Savage - will it be ok??

So i have my FLM savage ( http://www.rc-monster.com/forum/showthread.php?t=13463 ), and i've been thinking of leaving the 2230 where it is (in the LST) and going for a 1950/8 on 6S instead? =)

The problem is, i know little about how you go about choosing a lipos right for certain setups etc... anyways, here's the plan...

*FLM Savage (http://www.rc-monster.com/forum/showthread.php?t=13463 )
*Lehner 1950/8
*MGM-Compro 16024 Car Truck controller - but i'll probably use the 'air' style instead of the cube for space reasons... unless someone can give me the dimensions of the 16024 cube please? =)

**PolyRC 6000MAh 6S 22.2volt 25C pack (168x48x67mm)

*This is the part i need help on - i'm fairly certain it will work - but is there a better option to take?? I want balls, but moreso runtime - if i can get around 30 minutes and not be slouching round too much, i'd be laughing... how do i work out the runtime i'll end up with??? Is there another pack that would work better with the setup i wanna run?

Thanks guys =)

-daniel