Thanks all for your replies,
@Leslie : That Scott Sport frame looks nice, but the one I have considered is more the standard triangle shaped frame, with Rock Shox mount on the Top Tube and Seat Tube pivot. The idea is the massive 200mm diameter motor would sit as low in the triangle as possible.
Yes the config is unusual but I "wanted" to be able to :
go 80km/h on the flat with a lot of wind resistance
accelerate UP a 'jump' mound
have a COG toward bottom of seat tube to provide manoeuvrability
@MonkeyMagic : Crap, I have underestimated the battery situation entirely. I forgot I require batteries that can deliver peak/max current and not just meet the Volt/Ah requirements. I think my battery budget might have to be extended out to a months spare wages
@Bikemad : Cheers for the link to that post. I can't believe I hadn't seen that before. The Tyco Part number 770680-1 is exactly what I was after and I appreciate the sprocket list too.
I might spend a little while reconsidering as I have come up against a few hurdles I hadn't foreseen. Namely, how do I utilise EMF Braking whilst retaining the low-loss freewheeling of a std bike. Do I just use the standard Hyrdaulic brakes. Do I add the complexity of an electric clutch? Should I retain the pedals to limit the unwanted attention of Australian police.