https://www.facebook.com/marketplace...4-7133f4cef4be
https://www.facebook.com/marketplace...7-9a0ad66e7f8d
If you could find a pipe vice like the ones at the links above that would solve your question of how to hold the wood in place as you cut. The largest capacity I have found is 8" but very expensive if bought new. Down in the oil patch, I would think you could find them cheaper at pawn shops. And if you do find a bunch of them, I'd be interested in one.
Thanks,
Robert