Why is that? Are mechanicals less effective at lower draw weights? He is shooting accurate with the mechanical. Would a fixed 2 blade fix the drop problem that exists with a fixed 3 blade?
Accuracy is bow tuning and form
Broadhead accuracy is bow tuning
Penetration is blade angle and cutting diameter (assuming bow is in tune)
Mechanicals as a majority have large cutting diameter and flatter blade angle, toss in the loss of energy to open it and you are better off with fixed on lower poundage bows.
Another thing to think about is likely hood of a passtru. Fixed will continue to cause damage.