For 27t gearing is VERY
important as i'm sure you know
I usually aim for about 28mm rollout
The track i race at i would consider mid/low grip for carpet
technical but with a very long straight (we use the biggest indoor carpet track i've ever seen)
I'm using the mid span arms with the shocks mounted right out in the lower holes front and rear.
3rd hole in up front with yokomo hot yellow springs 12.85lbs
2nd hole in on the rear with yokomo blue springs 10.45lbs
as said next week i'll have moved to blue in the front to, but with the shocks right out (this set-up will very likely be too soft for you but might give you idea's of front to rear balance ??)
I will prolly also add roll bars and possibly take out some front caster by using spacers under the wishbones to liven up the front even more.
With carpet i'd also say that the softer tyres aren't always the best and often more grip can be found with harder compounds.
i'm not sure where you are at the moment tyre wise but i'd suggest around a 40shore to start with or possibly the proline purple's/double purples depending on your driving preferrences
hope i might of been of some help