Im using 9s with 3 however I bet you are OK with two you just wind em tighter as it is going to take the same amount of force to keep the trem "floating".

I don't know whether the distribution of force make a difference (i.e. having 3 contact points for the springs instead of two), Im not sure that it would effect playability as the amount of pull generated by the strings is going to be the same either way round.

Any one know for sure ?