I got a reply from Steve Pope, which clarifies quiet well the various option for V-Glide kits for HW97. Thought I might share it with you for whoever is interested:
There are a number of options available to you in the way of tuning kits, to improve your HW97.
Our tuning kit is available in two options, sub 12 ftlbs and high power.
In .177 calibre particularly, the 97 isn't capable of energy figures much over 12 ftlbs in it's standard factory format, (by this I mean with its stroke remaining unchanged.) so even the high power kit will only return very moderate figures 13-13.5 ftlbs on average. I am assuming, that the factory rifle has the same action stroke as the uk rifle, which has always been the case in the past.
We also offer a V-Glide kit, in 3 power options.
A V-Glide kit is a replacement piston, compression chambers of our own design, along with the additional components that make up a full tuning kit.
option 1 sub 12 ftlbs
option 2 moderate power,( standard stroke,) Option 3 high power,( increased stroke.)
The increased stroke equates to 8mm extra cocking length, this obtains as much capacity from the rifle as is possible.
This also means that the rifle needs to accommodate the extra stroke, and some alteration is needed to the stock inlet to allow the lever to travel this greater distance, and also to the lever itself.
Both modifications are straightforward to do, and we can supply details on how to achieve this.
The long stroke version can generate 15+ ftlbs in .177 cal and 18 in .22.
V-Glide kits are available on an exchange basis for your old internals or non exchange basis.
The long stoke versions cost £175 non exchange, £150 exchange.
In all cases, as a target/completion rifle, the sub 12 ftlbs version is the easiest to use, with minimal recoil and fast lok-times, though the long stroke high power version shoots very well also.
It would be the best result, if high and low power is required, to utilise the long stroke V-Glide kit, and have a second spring and guide arrangement to switch to for low power, that should work well.
Hope this helps,