It's been a while since I've posted here, also a while since I've ridden the bike. (Damn PhD getting in the way
The best cooling numbers I saw were about 700W (8deg drop, 1.2L flow). Done by measuring temp difference between entry and exit of the motor (to include heat loss from the tubing). This was however before adding the themal epoxy to the windings and the motor definitely cools even better now (I was seeing up to 25degC delta T between coolant and windings, this has dropped to 15degC max), I just haven't formally measured it since the change - I should probably do that. I wouldn't be surprised if I'm getting 1kW of cooling now.
I doubt my bike ever gets ridden for long at the 80% efficiency point, but then on my trails there's no way to keep 6kW on for long either!
Oh yeah, just to make it go faster I've added blue flames to the side panels