Well, sorry not to have contributed sooner! I guess if I wanted to do a first-class job on that mandolin, I'd consider a variant of fishin's carbon fiber reinforcement. I'd remove the fingerboard and reglue the headstock as cleanly as I could using whatever glue and those little dowels for alignment.

Then, I'd set up and rout or mill as much out of that area as I could for a really solid maple reinforcement right down the middle, hopefully running up the peghead and down the neck about the same distance. A good fitting heavy spline like that (approaching as close as possible to actually breaking through the back side) set in with hide glue should provide terrific strength without being visible when fingerboard and peghead cap are back in place.

Nice looking Dove Steve. I just got my '68 back in my shop for brokering/selling, and did a photoessay if you want to see the pics, let me know. Doves sure are showpieces eh? I hardly remember a single show I did with that axe that I did not get a comment afterwards on how pretty it is...