I bit the bullet and made up some aluminum mounts, for my 17 ft Tracker, and bolted them to the gunwales, for the Big Jons.
4 thumb screws remove them, with only the mount left.
I had Walker hand-crankers mounted to the very back.
You don't want them there. Giant PITFA.
Took the rear seat off the pedestal, and mounted an 18", 1/2" X 6" piece of aluminum to it, that I mounted 2 rod holders, and then milled 2, 5/8" slots to drop pliers into, without falling thru.