I want to run 4s lipos for a nominal voltage of 14.8v.

40000/14.8=2702 KV

So I would want a 6XL which would put me in the 95 amp range.
I would need a better controller the the 9920.
and I would need at least a 95 amp battery. So that is pretty much out. I dont want to upgrade my controller (yet) and dont want to pop for the batteries.

If I added 1 cell for 5s lipos I would be right in range for the 8XL.
3.7*5= 18.5 v
The motor should be able to handle roughly 74 amps.
9920 should handle the and 5s 8000 mah should cover any current I need.

Given me a grand total of 1300 watts. So the motors should be rated somewhere in the 1300 watt area.

I think I have it down enough to help a few people out. (I am getting asked all the time at the track).