Chloe, being a moody mare, has days where she's relaxed and stretches herself, but a lot of times she is tense and hallows her back. The tree fits fine there is enough clearance from her withers/pommel, it's just that her saddle was actually putting pressure points on her back. Finally we decided to A) get a new saddle or B) get a nice gelly pad. We decided to try plan b, since the saddle is only a year old and the fit wasn't horrible. So after a little shopping, I picked out a pad.
...and I LOVE IT! Chloe has never felt better. She is actually rounding by herself... before id have to work really hard to get it. Her transitions/canter... amazing. She is no longer in pain... the only times she gets tense and hallow is when she's confused or throwing a hissy fit. I'd HIGHLY recommend this to anybody who has a horse with back problems. It's a tad bit pricey and you have to take good care of it, but its so worth it.
Chloe had about 2 months off from the saddle because of her stitches and colic, she got a rare bacterial infection and a lot of proud flesh... hence my inactivity on this forum. So her back has had some time to heal. She just got back into work this week.