That's all good info above, but there's a problem I had that you should be made aware of. The hull panels on my kayak twist a bit in the area of the pedal mounting screws. So the axis of the studs (I used elevator bolts) was not parallel to each other. This made the mounting rails very difficult to install. When I first had trouble I should have drilled out the mounting holes, but instead I just forced them. Now I doubt if I can ever get them off. Next time I believe I'll use the external screws, as you stated they are the easiest to maintain/replace. The odds are this problem was unique to me since nobody else seems to have had it, just be aware.