I'll introduce the molded piece to Mr. Beltsander and remove all the excess material that will get in the way of my clamping operation. Then I have a perfect little caul that fits so well I can be confident about my glue-up:
Al I have to do is to squish the glue into the crack, pad the other side of the peghead and clamp normally:
I'm using hide glue, because of the instrument's vintage, the easy water clean-up and most especially because there is no tendency for the glue to "creep" under the high tension of a mandolin tuned to concert pitch.
The joint came out looking as good as before the break:
I was able to get perfect distribution of clamping pressure all the way along this carving without the possibility of crushing the soft cedar!