I've seen a few different ways of making a rear wing mount brace but I didn't want to have to cut anything so I used a R5.1 Lipo Standoff (Part #4699) and 2 - 2mm ballstud spacers, one on each side of the standoff and it fits perfect. I also used a 3x8mm BH screw on each side to hold it all together!

Source:

S. Borden