(yadda yadda)
Just posting to thank the group for giving me fresh perspective. Sometimes I get so focused on a problem that I kick the solution to the side so I can concentrate!
Here I was trying to figure out how I was going to get a router to (safely) round off the corners and the answer is to turn the router off and take a few swipes with just about any other tool ... rasps, sanders, handsaws, chisels.
The matter of rounded v squared tenon would seem to be an aesthetic judgement call. If I make the tenon a wedged tenon a little slop in the rounding process might actually work to my favor. Indeed, if I were to slit the tenon and drill an undersized hole, the wedging could be done with a dowel.
There seems to be some design potential here.
Thanks, guys. I think I'll go downstairs and play for a while.
Bill