Changed the motor and ESC, got a max 6 and a 4292 can in it. Motor and ESC much cooler, batteries arn't getting hot either. Thing flies on 6s.
However now the gearbox is cooking, temp gun showed it as 100c. Being plastic that won't last long.
Wheels aren't balanced well, it wobbles like jelly on WOT, so would be nice to find some others that are a similar size, but belted?