Anyone use an english shim pad under/over western saddle pad?

I have a horse who has “divots” behind his shoulders so I have a custom fitted and flocked County dressage saddle. No problem there but when I’m looking for a western saddle for trail riding, I need a shimmmable western pad (I tried the Diamond wool and it works really well). BUT…I have a Thinline pad that I used with my dressage saddle (before the custom fitted saddle) and I still have it. I’m wondering if anyone has ever used an english, shimmable half pad with a western pad. I really hate to buy another shimmable pad for a western saddle when I have one sitting in the tack room and they’re sooooo expensive! Thanks!
Also, I do trail ride in my dressage saddle on occasion but we want to try western dressage and I like using a western saddle once in a while to just chill.