With AirHauler, I have been taking off above max gross weight.  So, during one approach I lost track of speed and did not hear the stall warning; consequently, I fell to the ground such that no amount of power was going to get going again.  Is there a way to calculate stall speeds?

 

 

How much over MTOW are you departing at? Here are the numbers from the POH for stall speed at MTOW (8,807 lbs.). Not sure if that answers your question, but should give a good rule of thumb.