I don't have LOTS of experience with the TX, but........

Mine's a .177 HC (Mark 3) and the original top hat was the large heavy one, as pictured. I think .22s will have a different size top hat as standard? Maybe also the full length ones? Replacing this with the Delrin item and less shoulder height reduced preload and, of course, all-up piston weight. Then increasing preload at the back restored the power and gave a much nicer and quicker perceived feel.