Very nice enclosure, I like!
I would probably have put 11 X 12 inch flexwatt under each unit for a bigger hot spot and more help with ambient temps.
At this point you might research running a 3 inch strip under the front of the enclosure to help with your ambient temps on the cool end.
Maybe put the 4 inch up front under the cool end and put three 11 x 12 pads in the back for the hot spot?