I used (black) locust for most of my pegs - it makes awesome pegs that hardly ever split. Two to one, better than white oak. When you tap the dry locust pegs against each other, they sound like chalk - that's how hard they are.
I read somewhere in the back issues of the TFG journal that hornbeam makes the strongest pegs. (I think they did some testing and had a chart of the results?) However, I was under the impression that the hornbeam they were referring to is what we call (in Eastern Kentucky) "iron wood" - probably what you are describing as "muscle wood".
So basically, I've skirted around it, but haven't answered your question at all - but I'd be keenly interested if someone _could_ answer your question!
my timberframe project
