I've had some pretty good luck in sealing the tranny. That's another mod I always do.
I use silicone on the mating surfaces during assembly, then use rubber sealed bearings on the output shafts.
I haven't experimented with different vicosities on the lube, but I use Lucas oil stabilizer. I think maybe it's a little thick, but seems to work good for gear oil.
I don't think I want to vent. Dust and abrasive material is the enemy of gears and bearings.
Before the new E Maxx info was released, I was pondering a FLM case to dissapate heat and all steel gears. I think I'll just start with the new E maxx instead.