Thinking of fire...maybe working in App fireball tower?  The core of the build is pretty fast since you already have EV out for Buff beams.

Basic concept is Oil traps and SAMs and with the long open lanes on this map, is screaming for it. 

South Island needed a Mortar to be safe as well (sad).

Note, East Island was the only one that had any trouble.  We had three SAMs there, but the mass of mobs overwhelmed them, so we put a Mortar there to help with the number of mobs.  The other three islands simply cooked!  The trouble right now is the number of skeletons that the mages make and take targeting away from the SAMs, it just slows them down a bit.  Where we can, adding in some inferno traps to help with that.  Maybe we don't need shroom pits, but for me lately they are a standard in all builds, because they create weakness in enemies and fire in all directions with strong nuetral damage, they are kind of a SUPER tower, so always want to play them if we can, but if you're looking to modify, then you could get 20 DU back by dropping them.

Time was about the same as other builds...