Spring room? Owwww I am going to have to think about that really carefully. Shorten the stroke to get a better swept volume to TP volume ratio means there will be less space between the inside face of the piston and the back block to get the spring into... which means ... a shorter stiffer spring than if it had more space? Doesn't the HW95 have the same stroke as the HW80?
The ProElite is an extraordinary rifle. Not sure how it compares in performance terms with an 80 but probably it's by far the nicer rifle and I've never shot anything as accurate.