that's what i guessed :bluethum:
it's easy - look at the HP curve, and the point with the STEEPEST slope is where the engine makes peak torque. from the green curve, looks like 36.5mph, which now you just gotta flip to an rpm.
actually pretty easy since the bike redlines at just shy of 70mph-rpm. so, find the redline of your bike, and cruise at about half of that (since 36.5mph is about half of 70mph) :bluethum: