-slide in O-rings onto the IB just in front of the hop up unit to have it sit back more. And if it moves too far back, shim the gearbox with tape or something of the similar.
or
-Modify the tappet plate like so:
http://www.airsoftcanada.com/showthread.php?t=92666
or
-Get a longer air nozzle that is long enough to reach but not enough to cause misfeeds.