I want to put a paddle mount on my SUPs (P65 RR 11.5/12.5). There are rails (U/C channel) on both side of the board and some of the reviews say they can be used to mount a seat. Are the rails for some standard-sized mount? I’ve done quite a lot of searching and can’t find an answer. These are the first SUPs I’ve owned and I have not seen similar rails on any other devices. The scotty mounts look like they could be a fit. Thanks for any feedback.