My saddle appears to fit my new mare fairly well, she has plenty of clearance, doesn't rock back and forth, and isn't pinching her shoulders. The problem is that the saddle tends to slip to the right or left. Is this a saddle fitting issue? Or is it just because my mare is a 2 x 4 right now? Is there any way to stabilize it? And yes, I have made sure that the girth is tight.
I actually like the way the saddle sits on the horse. Looks like nice even distribution. It doesn't look too wide which usually is the cause of side to side movement. Like MIE said, maybe the panels are a little round and contributing to the side to side movement. It can be helped somewhat with a half pad with or without the use of shims. To find out where the uneven contact is, try putting a clean white baby pad under the saddle, leave you horse's back a little dirty, ride in it for 15 minutes or so and then post some pics of the underside of the saddle pad. Ideally it will look like an evenly dirty saddle pad. Dirtier areas indicates more saddle contact and pressure while clean spots show no contact at all. You can use that to see where you need to use padding to help the fit until your horse fills out a little more.
My friend who is a Saddle/Maker fitter for Schleese reads pads, and I love how quickly she can tell you where the issues are - I have another friend who works for County *the one I told you to contact* can do the same thing.