On my
Wildcat, the Hammer Spring Tensioner (HST) was accessed by taking the stock off.
The tension screw is about 1/2" across, made of brass and facing backwards (opposite direction to where the pellet will fly).
My UK version has a brass lockscrew with a broad slot, screwed over the top of the HST and this was held in place by locktite.
I released the locktite by heating carefully with a hot air gun. I would have used a hairdrier, but I don't have any hair.
On my <12fpe gun, it took about 1.5 turns to change the power by 1fpe. In for up, out for down.
If you are dealing with a power drop on your gun, it may be that the barrel has become misaligned with the transfer port.
Unfortunately the WC does not have the ball and detente barrel retention system that the Impact seems to have.
travels4fun dealt with this in this:
http://airgunnation.dev/topic/wildcat-shroud/ thread. Compared to travels4fun's barrel, mine has a very poor indent which may explain my power variation.
It would be better if the indent was a machined 'bowl' shape into which a round-tipped grub screw could fit. That would fix it.