Fat rider on a short backed horse problems....

This is going to be a bit rambly as I work through a few thoughts all surrounding my current tack choices.  This is all kicked off from a rub Uno got on a long 2+ hour walking hack last week.  It was right at the end of his back where his saddle pad seam sat.  

It is impossible to keep stuff off that spot, because even if I put his saddle a bit further forward, it slides back (then doesn't move) due to his massive shoulders. I have spent the last few days with different pad set ups, and different tack options seeing if anything looked any better.

The issue is that from the side it looks like we have withers, but from another angle, you can see that his shoulders muscles are large and rounded.

Note one:  Although this place was a little warm and sore after the long ride last week, he was not sore there within an hour of the ride being over and has not at any point seemed sore to me or my trainer.

Our usual setup - an AP pad with an old-school thick wool pad.

Part of the problem (dem big ol' shoulders)

Yesterday, I tried a different pad setup and wow that was not great. First off, despite a tight girth the saddle felt a little roll-y.  And all the pads slipped.  The saddle did not move but the pads slid WAY back.  Interestingly, this did not happen in my lesson where I used the fleeceworks half pad with a different AP pad and no thinline pad.  Things to ponder.

Before the ride.

After the ride.

Pads off.  It is hard to see but the saddle itself has not really shifted much at all.

I am not sure what to do from here.  We do have breast plates that we have used on cross country, but the saddle itself is not really shifting, his shoulders are just pushing out the pads.  I made this choice thinking that going down in pad size would give his shoulds more room, but that seems to have made it worse.

I am dreading going down to the saddle fitter because I cannot afford another saddle.  I am also aware that as an overweight rider, things like saddle fit become more important.  I am not sure what my choices are going to be but I take a little dig around my collection of half pads and see if there is anything else I want to try.

We did jump this for the first time together yesterday and it was perfect!