You don't mention what type of boat you have, but the driftmaster clamps will mount to a 7/8" or 1' round rail if your boat already has rails. if your boat has the track along the top rail to mount accessories to, you can make a mount that will accept the driftmaster base, and then the entire rod holder can be placed anywhere along the side of the boat (front to back) and be used for various methods of fishing (spider rigging, pulling cranks, longlining, etc). You can even get trolling racks that will go across the entire width of the transom if that's the style you want.
GO BIG ORANGE !
I meant to behave, but there were just way too many other options available at the time.