A system of two hour wars would be very welcome. For those of us who work long hours and have family commitments, finding a 4 hour slot to devote to a game isn't easy. Wars r fun, but for me, they just aren't accessible atm. As for xtals, don't allow their use in 2 hr wars or limit it to once.
Even if you can't commit to a 4 hour war everyone's admitting that most wars are only 2-3hrs long anyway. So just join a war anyway. Who cares if you can only be active for half of a 4 hr war I've done it just make sure you won't be a leak and your fine
2 hour wars are too short. The clan with more xstals will win. Provided there would be good matchmaking on the devs' parts.
2 hour wars are too long. When the matchs ups are un even, its over in 5 minutes even if everyone is active.