I tried to answer that in my last post by saying that I personally found no difference in the cocking, firing or accuracy of my 77 with the old Venom kit or the new V-Mach kit.
The other work inside the gun Steve will have learned from his Dad anyway.
Surely the proof is in the pudding ... ie the end result.
If this was a car engine I suppose you put the pedal to the floor and you see what the max power is ... or top speed ... so you have a figure to compare like with like. So is this new one better than the last one etc.
... but once a gun cocks as smooth as a smooth thing ... and it fires with a fast and minimal thud ... and you are getting groups that are as tight as is possible given tolerences of pellets and the thing pulling the trigger ... then you've reached a point where it doesn't really matter ... and/or it's not possible to tell the difference between the two.
I think we've reached this point now with kits from V-Mach and Welsh Willy etc. I've said before that you can then start buttoning or going to the extremes that Bigtoe does to satisfy personal curiosity ... but you won't get 'noticably' any better result.