WoodButcher and CW,

I thank you both very much! Concensus seems to be:

1) Don't cut a matching mortise, just drill a round hole.
(WoodButcher's use of the heated tang to burn-in and seat sounds good,
a nice refinement to the round hole approach.)

2) Don't heat-shrink on the ferrule, a press-fit will do nicely.
Inserting the tang will expand the wood against the ferrule. I plan
to line things up and then use a manual arbor press to seat the
ferrules.

3) In case of error, epoxy is your friend. How true!

This new plan is much better, particularly in terms of abandoning the
idea of using a small chisel to try and cut out angled, deep
mortises. Yeesh.

I thank you both very much!

Dave