OK, new wrinkle.

I stopped by the fun store and it turns out the original owner had commissioned another barrel for this underhammer. A fast twist 45 sporter weight, with iron sights. Mine now....

So.....

Considering the heavy barrel was tapped for a scope, and has holes in it at the breech end, I'm thinking now that a sight like this would be in order:

http://4.bp.blogspot.com/_j7PMWDJke...hjo/s400/Billinghurst+action+closeup.bmp

Then I can get the sights "barrel specific" and use the sporter weight for hunting. Will probably replace the rear sight on the sporter with something like the rough and ready or express sights.