I have thought about seat savers for making my basically very comfortable dressage saddle stay comfy past the 4 hour mark on back country trail rides:)
It seems to me it matters what job you need the seat saver to do.
If you have a bad back and want cushioning for an hour’s schooling, it sounds like the gel pads like the acavallo are the way to go (haven’t seen them IRL yet).
For long trail rides in my particular saddle, its more like softening things and preventing rubs, so I’ve been thinking about sheepskin because I feel like 4 plus hours on gel in hot summer weather might be counter productive.
But I’m also nervous about any seat saver shifting in a spook, or going down a steep hill. I’ve been on mountain trails around here where if you lost any traction in the saddle you’d go over the horse’s head.