My mooring cover is also very tight.
I have these mounted with the flat side out, and the bulk inside, opposite from what the picture shows. I will take pictures. The holes for both the bolt head and the lock nut are countersunk.
Like Johnathan, I didnt want to drill holes in my 2009 toon, and would use the drift master square rail mount ( I did use wing nuts on one side of the mount bracket), at the cost of 8.99 for lil pro, and 9.99 for the pro.
These answer all my questions, I even have two mounted at the back of the toon for trolling. The mount is very streamlined on the outside so my tight Mooring cover is not affected, yet easy to set up and fish with. When not needed. a twist, pull them out, stow and they are out of the way.
Also the screw and lock nut are stainless.
I do have a bundle invested in drift masters, and will be using them on my new 1989 Tracker v guide special boat
For square rail, these are the easiest and best.