Okey dokey, pig in a pokey...
SO I've installed the following on my SRS A1 Covert 16"=
W.A.S.P adjustable weight piston with full airbrake and heavy steel outer tube (heaviest of 3 supplied).
3 preload spring guide washers that come with the above piston.
Rapax APS2 Style Spring (2+ Joule)
Maple Leaf "The Last" hop unit.
Maple Leaf 410mm Crazy Jet barrel.
Maple Leaf "Maximum Range" 50 deg bucking.
Chrono on 0.43 = 340fps (2fps deviation going lower not higher)
Hopping perfectly in my limited range of 30m (so not a true test of accuracy etc but bang on the money where I was targeting)
Obviously none of it has bedded in properly yet but very pleased with the results.
This spring is very easy to cock even with the preload.
In the end I bought and mounted a VISIONKING 1.25-5x26mm - very happy with the choice, eye relief, clarity, etc...
Interestingly (although limited to the range I can shoot in the garden) I didn't have to dial it in! Crazy... it was just exactly where I dialed the hop by coincidence. I did the hop before I looked through the scope. No doubt on site it may need a click or two I'm sure.
All in all I can't wait to try the rif out this weekend coming. I'll report back my results.
Currently 3D printing something to meld the suppressor to the foregrip. I'll get a photo once mounted. Had an issue with the suppressor I bought, it doesn't want to screw on the whole way (Grrrrrrrrr). I may buy a 14mm ccw tap and rework the threads on it at a later date. It screws on enough to work but is fugly hence the model I'm running right now to fix it - it should work well enough for now.
EDIT: Oh and the Match Knob is a very nice ergo upgrade.