I have a Steve Pope tuned HW95, bought second hand, and I've never looked inside. Whatever has been done makes it a super smooth machine. Its very accurate.
Its a basic Luxus configuration stock with HW Silencer which makes for a very light weight combination. I really love it and not going to change anything.

However, its the weight of the rifle that makes it hard to "keep it there". All the lighter rifles I've ever had, highly tuned or not, when spring powered just can't match something with more weight. I think a certain mass to a combination makes a fundamental difference to repeatable spot on accuracy.
Heavier HW's, Air Arms, Pak 91/93, all the best behaved all, have 8fts plus plus weight. I much prefer to shoot a sporting light weight rifle but resign myself that they just can't compete with something weightier.

We do our best to tune to silky smooth but the physics are against us.