With regard to your girth (or technically, lack of it) did you keep your breastplate on?
was that the woolback girth ? Think there was anything different you could have done which might have helped if you could go back in time ?
IMO, the issue was the saddle. George is still going in a treeless, as the funds to provide both geldings with new custom treed saddles was not in the budget at once. Sultan showed lameness issues first, so got the new saddle. This was the first time George attempted a 100 in this saddle, which does not have the ability to change the rigging to center fire.
In George's previous 100 attempt, my DH started with his Bob Marshall in the normal rigging then changed to the center fire rigging about mile 70 because George was starting to get rubs. I likely would have finished the ride with a girth attached had I been able to change the rigging on the Torsion in that way.
I personally think that eventually treeless saddles just don't distribute the weight evenly or enough, so the horse starts to do weird things with his back, which translates into the girth moving in ways it wouldn't ordinarily. Sultan has had ZERO girth issues since changing to the treed saddle, and I think we had tried every type of girth or rigging imaginable with him when DH was still using the Bob Marshall (he was coming up girthy even at lesser distances, but never showed apparent back pain).
Just goes to show how much a horse will tolerate for us!!