I put DRs on a 14' aluminum boat once, had a heck of a time turning as it acted like fletching on an arrow keeping the boat straight.
Having said that, on my inflatable, I mounted the downriggers to a 2X10 that went across the gunwales. If you put a through bolt through the back bench seats to attach the board to. I think they make pedestals that would stand tall enough to get your DR to railing height.