Powermatic feeder slipping

[D6c]

I recently got a 3-wheel Powermatic feeder to use on my jointer and on table saw later on.
Feeds ok but I'm having trouble with the adjustment slipping where the head clamps to the horizontal round ram.
I get the wheels set level with the table, tighten the two pinch bolts good and tight, and set the height so the wheels are about ⅛" lower than the board.
After running one piece through, the feeder isn't level any more ( the leading side pushes up).  I marked the round ram and pinch clamp and you can see that it's moved.  Hate to tighten it any more for fear of stripping the threads.....frustrating.
Thought maybe I was bottoming the travel on the wheels but I checked and they have nearly ¾" travel.
Any suggestions?

[farmfromkansas]

My Grizzly 1 hp was having trouble with the tires slipping, and I waxed the table of my shaper.  Really helped.  I do have to check the adjustment on mine regularly. Probably tighten it plenty tight.

[D6c]

Tried it again this morning.  Tightened the snot out of it but it still slipped.
Think I'll call Powermatic tomorrow and see what they have to say.

[tmbrcruiser]

I have a powermatic power feed on my spindle shaper. I keep a heavy hammer by the post and use it to tighten or loosen the hold. No problems slipping or stripping.