I see you're already decided against this pad... I think you're right... here's a couple pictures that show what I think what the problem is with this one... It's too thick to allow the saddle to fit down on him all the way... I've lightened and painted on your picture to show the excess 'dead air' under it in transparent ... that peach part of the saddle should be bearing weight, instead, all the weight is going to be on the ends of the panels, painted in brighter red.
Here's a pic of mine on Bay, not from the same angle but hopefully close enough to see, it's the best one I have. He also has all kinds of pad under him, but, presumably, the right amount for the saddle to fit his back.... the panels on the saddle match the angles of his back and are sitting flatter on him. There's not so much dead air under the saddle.
The cashell cushion I have does not come out so far around the back of the saddle. If I don't get it on just right the edge of my saddle hangs off.
I swear, I'm sick of this, I'm ready to chuck the whole mess.
Becky