I'm facing the same problem. I have a fiberglass boat and mounting to the sole or floor isn't really a good option, as I would have to through bolt through the hull.
I made a pattern of the area in front of the front seat (my seat is mounted on a bench or thwart that runs all the way from side to side). I'll use a piece of 3/4 ply and seal it in polyurethane. I'll mount the rod holder to this and just drop the whole thing in. With a bucket of minners and my feet on it, it won't/can't go far. Nice thing about this is it allows me to pull the rod mount out quickly and store it if I'm doing another kind of fishing.
Quit complaining about the color, just pull up your skirt and fish! -- snagged