Hey guys!
Just stumbled on this issue... it gets discussed about every other week on "that other board," so I didn't think to look for it here.
I have been running an UltiMak on my SAR-2 for a months now. Much of the heat-buildup issue is overstated, usually by folks who have never used this product for themselves. It takes a lot of rapid fire to get the mount heated up, and by that time the lower HG is too hot to handle as well... I've got a $30 Simmons red-dot on the mount, and it has never had a problem handling the heat. Even when the mount gets hot, the optic stays cool. If you're still worried, you could always go with a "ruggedized" optic like an Aimpoint COMP ML2.
This sight setup is probably the best fast-acquisition system for the AKs out there. And yes, I've owned the infamous Kobras. They don't hold a candle to the UltiMak in terms of comfort and functionality. Especially if you're a cross-over from the AR world and like to co-witness your iron sights with your red dot.