I'm looking to install downriggers on a 16.5ft Smokercraft. There appears to be enough room on the gunwale to install a Scotty swivel mount (http://scotty.com/fishing-gear-equipment/downrigger-mounting-systems/1026-pedestal-swivel-mount.htm).

They recommend using a backing plate, which makes sense. But as best I can tell, there is no way to access the underside of the gunwale (absent cutting an access hole in the aluminum, which I do not intend to do). Same problem if I wanted to use the right angle side mount (http://scotty.com/fishing-gear-equipment...unnel-mount.htm)

So what's the recommended solution? Just screw in without a backing plate?