Damn Bones bottoms are too short for thunders? I’ve been using hard Bones bottoms with great results thinking it’s been keeping stock height. I’ll put bottom bones washers in if that’s the case.
You'd need 2 bones washers in order to reach stock thunder bottom bushing height...(including washer)
If you are currently having great results as is, why change? If it works, don't fix it.
A while back I ran 8" Thunder TIs with bones softs top and bottom, no washers, on an 8.25" and it worked like magic.