On my +4 I drilled through the ash frame and used nuts & bolts but then I used Simmonds posts that are quite different being a large round foot so very stable. My first mog a 4/4 had the standard feet already fitted & they tended to vibrate loose. The disadvantage was on the drivers side they were a ted close to the screen so with the screen up the knobs on the uts tightening the screens need to be in just the right place or they fouled the screen.
Where can I find the Simmonds posts that you mentioned?