gsxr1100:
The reason thay they don't allow is goes like this: when the clutch is disengaged, there is no chance of drive power getting through as you start. With a hydrostatic, if the control pedal were pressed, the brake is in a contest to see if the hydro drive or brake wins. In low range, unless you push really hard on the brake pedal, the hydro will win and it will move. So a brake interlock would not provide the required lawyer-proof security. So neutral is the safest bet. My old tractor would allow you to start if the hydro lever was centered. It had a detent position so that you knew you were centered, but that would be hard with the pedal control.
paul