Thermally I have no concerns, the EVO2 is rated for -18°C (0°F) to 60°C (140°F) operating temperature. The bracket design provides an air gap from the transmission/case, it does not act as a heat sink(draw heat from the engine) and has significantly improved air flow over the stock location.
I avoided an unsprung (wheel/swingarm) location or connection by design. Even though we run these EVO2's on our dirt bikes where they get the crap beat out of them the sprung (frame) side just makes engineering sense. The bracket didn't move or swing up much prior to connecting the battery cables and it's not going anywhere once connected. I will run my old GoPro down there just to be sure.
All that being said if I make another one I'll probably use a full width aluminum or stainless steel stock VS the bar stock under the battery and to the mounting bolt. Maybe lower it 1/2" on the bottom increasing the brackets depth but I don't think ether of these modifications is required. I'll upgrade to stainless steel ties/straps sometime in the future.
Now if I had decent welding skills...but no, just a hack.
Cheers,
Kenzo