I also would have just stapled my support wire to the tree. If I'm in trees, I bring a satchel of snares, a bundle of precut support wires, a pouch of fence/poultry staples, and a hammer. In trees, there is rarely a reason to carry support stakes. I go straight to the tree. It's one less thing to carry, and it's also one less unnatural thing (if that's how you look at it). Staple support, anchor snare around tree, set snare, done. You don't have to introduce something new, and you don't have to hope you don't hit roots. Simple. If you're going to snare here for the foreseeable future, rub trees are worth putting the permanent supports I mention, because they'll use the same trees for years. They'll be there next time you return.
Where supports come into the picture for me is when I'm in bogs and thickets that trees are spaced too far apart. Supports work there, but if there's a lot of tees, they aren't necessary.
One last thing: When setting rubs I want it to hug the tree tight. Picture a hog walking up and rubbing---he's going to literally be rubbing up against the tree. I put my snare on one side of the tree or the other, whichever way it appears they're walking --away from the mud hole.
Good luck, keep us updated
If you can either quickly or quietly switch out shells, you can bring home almost anything.