I use either the large or medium Robarts, depending on the application. 1/4!QUOT! of balsa is probably enough for most, but if its a really large surface or very high speed, I'd use the large size hinge points and very hard balsa for the 1/4!QUOT! (and be absolutely certain it is anchored in VERY well, distribute the loads). Just be certain that the hinges are in such that they will NEVER come out. I proof load each surface after installation and have never had a failure. Pull like h e l l on them!