I just went through this ordeal with my Extra and trying to install hinge points. This is the conclusion I came to.

The hinge points work best when there is enough wood to cover the barbs on the hinge point itself. Many elevators and H-stabs do not have a "deep" enough piece of wood, except maybe on the corner by the fuse. Therefore, the hinge point goes all the way through the wood with the barbs sticking out into dead space with nothing to grab onto. All that is holding it in is the epoxy and the smooth tapered section. Not enough in my latest experience. Plus, Epoxy does not stick to plastic.

The flat hinges seemed to be a better choice in this application. Also, CA is a better choice to glue them in. Rough them up a bit with sandpaper and clean them with alcohol either way you do it.

As far as getting them to fit nice and flush, here's what I was doing. Drill your hole for the hinge point. Then go a couple sizes up in drill bits and drill just the first 1/8" or so. This will enlarge the hole enough to let it sit farther in. Keep going deeper if you need to.

Good luck.

Mike