That would work but eventually wood's not going to make it.
For a while I bolted plywood across the safety bars (raised up) in my rack and used knee wraps to wrap a dumbell to my ankles and did the movement...not the best method to attach. Needed a pad under my hips. It worked Ok on the extension part. The decompression/swing under part not so much. I like to train in circuits and it limited that so I cut it out pretty quick. It was close to the method this guy uses but I did it from the side of the rack so my hip weight was over the safety bar.
