Note - bars DONT have any better engagement as alot of people try to argue, they are exacly the same unless the end of the bar is just cut off flat. If thats the case, it effectivly has 4 teeth, as theres 4 points all at the same distance from the centre of the bar. That makes it much worse!
Keep as much weight around the outside as possible, that will make a HUGE difference. Also, and obvious one, to increase tip speed (add more energy) and keep good engagement you will want to increase the diamtre. 360mm, 2 teeth, 4.4kg disc, 3kg of that around the outside 3500ish RPM 4hp motors- sound good?