I agree and this is half the issue, But I was thinking more of piston nose extensions to shorten the stroke to volumes optomised for Uk power levels as well. And springs selected for shot cycle (oftern softer and longer for larger bores to counteract bouce), and possibly superior quality piston seals.
However, if you have a lathe, some skill and some idea of what you are doing, I'd suggest you could get 90% of the benefit yourself for 5% of the cost (and your time, of course)