I preshape them to a nice bevel,wrap a thin block 1/4 x 1.5 x 3 with plastic wrap, and clamp the end down with the block really good first.
I have also gone to taping grip overlays with masking tape where they go so they don't slide as much.
That said, I STILL sand down into the limb glass to get it to look decent.
I have heard of putting a pc of clear glass under the overlay , but haven't tried it yet.