(something i got from somewhere)
How to alter your Yukon Hyperextension Bench so it can be used as a Glute Ham Bench
Out of the box, it's not a Glute Ham Bench at all, but rather, a hyperextension bench. The pad is not solid at all.
Rebuild the pad by taking two 12" circle 3/4" plywood and cutting it in half. You will end up with 4 half moon shaped pieces. Attach those to the plywood base of the pad, one on each end, the other two evenly spaced out in the center. Use 1"x1"'s and screw them across the plywood “half moon’s” to form the underlying hump. Visit a foam store and get some hi-density 2" foam cut for cushioning. Pick up some vinyl for the cover.
The toe plate is also too small, weld steel plates onto the existing structure so it is about 13" or so long. The toe plate needs to be bigger than your foot to allow for maximal calf recruitment from this movement
It's an ok setup, and works (quite well really) if you want to put the work into it.
If you do not want to (or are unable to) put the work, or really like professionally made machines, check out
www.sarden.com. He just came out with a GHB which is well made.