I have a Bob Marshall treeless barrel saddle I'm looking to get a new pad for. My mare is somewhat short backed. Suggestions?? I've looked at Saddleright and Skito but hoping I can get away with spending less than those would set me back. Also, I'm not actually running barrels on this horse. We trail ride and do fun shows, but due to some chronic pain issues I have I prefer to ride treeless. I ride a couple of times a week and weigh about 140. I'm just throwing out as many details as possible hoping to get the best feedback out there. TIA!!

I ride in Bob Marshall's. CSI or SK Spinal Relief are my go-tos. Both are pricey, SK pads are a touch cheaper. They run about $300-$500. There is a Used CSI Pad page on Facebook, but there's been a lot of spam on there. You want to ensure there is clearance and you're not sitting directly on the spine. 

I have used Professionals Choice HD, Classic Equine w/impact shield, ThinLine and Saddleright. By far my favorite is Saddleright. You could probable get a decent used on for $250-300. Well worth the money. Because of my mares build I do get the Legacy. IMO I would get that anyway with a treeless even tho SR would tell you its not necessary. 

5 Star 7/8" all I use with my treeless.  Yes they are pricey but well worth it IMO.  For a short back horse you can get a 28" 

I ride in a Bob Marshall treeless and my little horse has a short back and thick withers. I needed something that was short enough so that it wasn't going over his butt but also not built up and not too thick otherwise the saddle was slipping. I am using a Reinsman. It has kind of a waffle style neoprene underside. I can't remember exactly what I paid but it wasn't over $150 and I love it. I'll see if I can figure out exactly which one it is and if not, I'll take a picture. 

I can't find any tags on my Reinsman saddle pad so I took a picture. It's nothing fancy. It's not too thick--it's flexible so it conforms to his conformation. I'm asking hubby for a backup one for Christmas because I like it so much.