Let me revisit my opinion of the FB2. As I said, I bought it to moderate and compliment my new FX Wildcat BT compact 22. I liked the idea of keeping everything short/compact.
When I originally put the FB2 on my wildcat, I had it tuned up to run slugs. Reg set close to 150, pushing 23 grain slugs 1025fps. That was LOUD with the FB2, but the Sumo worked great.
I've now tuned it down for pellets, reg set around 95, pushing 15.9g pellets at 900fps. The Fatboy2 is working great with this tune. Still not quite as quiet as the sumo or tanto, but acceptable moderation for sure.
I think DonnyFl makes great products, but the marketing going on via some of the airgun youtube guys is misleading regarding the FB2.