There aren't many resources out there that I have found giving exact dimensions for mounting the electric speed brake but 2 very important rules apply. It MUST withstand at Least 95kts of indicated airspeed yet be weak enough to shear off in the event of a belly landing. I've decided to make a 1/4" thick ply block that will be floxed in place and covered with 2 plies of glass much like the trim lever is mounted.