RE: Engine bogging at high pitch
You didn't mention how many degrees of pitch you have dialed in at the top and the bottom.
Your engine has just so much power, say to turn 600mm blades at 11 degrees at 1900. So if you have 12 degrees set in, all your governor can do when it detects a drop in rotor speed, is to open the throttle fully (which it may already be). But if the load (more then 11 degrees) is more then the engine can deal with at wide open throttle, then adding a governor and setting it to 1900 does not mean you will get more power to maintain that 1900. All it means is that the governor will open your throttle to its wide open position.
The governor will only open the throttle to max open, it cannot make your engine develop more power at that opening.