Thanks Chris,

I think I'll just use some standard SS socket head screws. I have never liked the button head screws for the reason you point out. I bought some SS washers of the same size from McMaster Carr so I will put those large washers as my thrust spacers as well as on the screw head side and locknut side of the mount. I like having the area of the washer to spread out the load so I don't crush my ply/CF.