By 'at the base of the tree', where exactly are you talking about? On each side of her withers where the fork of the tree meets the bars like where the scars are on this horse? (you can see the small white spots by his withers)
I do have a very thick foam pad laying around... I'll try that one to see if it helps.
Ha, it actually looks a lot like the CSI pads on that link...
Could be one, but it isn't mine, so I don't know for sure. I'll have to look for a logo or tag when I put it on.