Hmm. That might just work. If you could, though, I’d leave that until you’d completely given up on other saddles. It would mean that you BUY the saddle, and then pay to have the tree shimmed (unless saddlemaker is offering to do the work gratis, which it sounds like he may be), and then hopefully that works. If it didn’t work, you would then have to sell the saddle before you bought a different one.
Also, if the saddle really shifted, you could be looking not only at a bar angle issue (thinking of the Wintec colored gullets in english saddles that you can change) but a rock issue.
Rock is like the ‘banana’ shape to the english panels/western bars. A tree can have ‘more rock’ and be more banana shaped, or have ‘less rock’ and have flatter bars.
You said that the saddle shifted back as well as side to side, I’m not sure but there might be a rock-in-the-bars fit issue as well. Possibly the saddle you have, that shifted, has too little rock for Mac’s back. And the tree would have to be shimmed to correct that problem, too, before it was a great fit.
You found that the tree in the too-big Martin Wade saddle was very stable.
I would contact the Martin company and ask them about the specs (and the maker of) the tree in THAT saddle. Whether you find another saddle like that one, that fits your butt, or you have the tree shimmed on the one you have, you will want to match rock as well as angle. It is quite possible that you could arrange for a tree like the one inside the Martin saddle, to be available to the other saddlemaker as a template while your tree is being shimmed.
I rode in it in Bryan Neubert’s clinic and mostly liked it
Is there anything else about the saddle that you weren’t crazy about other than the fit for Mac?
I remember the other saddles as having saddle strings that were just on a D screwed into the tree. I would take the opportunity while the saddle was being shimmed to change that- if you ever got your mecate (or a saddle bag) that was tied to the saddle strings, caught on a tree branch or fence, it would pull the D-attachment screw out and strip it if the saddle string didn’t break first- you can’t really repair that.
So…where I would go next is to the tree inside the Martin Wade, and find saddles to ride/try that are made to the same specs, but with a smaller seat size.
It may mean a lot of emailing or calling tree makers or saddle makers on ‘available’ used saddles to find out just what’s inside. Most saddle makers are quite knowledgeable about the trees, but some more so than others. So while it sounds like a mouthful, I think it would work pretty well to cull out saddle-tryout possibilities.
But at least at that point you’re not shooting ‘blind’, and can start with something that will very probably fit Mac so you just have your own butt as the variable.
And…it IS possible to change out the ground seat in a saddle. If you find something close, a saddlemaker can take out the skirts/seat and re-do the ground seat to YOUR pelvis. Probably not the best answer, but definitely possible.