Orion ED 80 Focuser Slipping

I have a new Orion ED 80, the optics are great for the price, good star test and little false color for the price. I have a problem and wonder if there are any fixes. I placed a Televue .8 reducer & 20D for imaging. Images taken up to 40 degrees stay sharp and in focus for 3-4 minuet exposures. However when imaging above this the focuser slowly slips and images go out of focus. I have tightened the tension knob on the scope to maximum finger tightness and it still slips. The slipping is visible through the camera viewfinder @ 2.5x during a 1-2 minutes of viewing. My though is any modification to the tension adjustment or tapping a hole thought the focuser's base and applying a brass or nylon screws to lock against the focusing tube to lock it in place. I would appreciate any recommendations as I like to image above 45 degrees, preferably above 60.

Thanks

Sam

1. polish the drawube flat surface
2. tension is actually adjusted by 2 small hex screws around the big adjustment one.

After that stock ED80 focuser holds my 20D and 0.63 reducer just fine.