Something just doesn't seem right with the amount of power required to get this thing moving, that's with no passengers and half a load of fuel.

Are you using the default flight model files or the ones from the optional patch from Bernt Stolle?

Bernt Stolle's.

I'm always running her at close to MTOW and it's true, she needs quite some throttle (40%+) to start moving. Could be a tradeoff to achieve the braking power of the prop in low torque situations in flight. But that is just a guess of mine. FSX's ground friction also is a thing being too high, so maybe it plays a role too.

 

Maybe you could alter the

static_thrust = 85

value in the aircraft.cfg to a higher one. Be aware that this might affect things on the flying later, namely that mentioned braking ability.