Almost everyone who reviewed the AGM Sten MkII said it had a fixed hop. When i opened it up today, i found out the hop assembly had all the parts necessary for it to be adjustable. Only some tweaking was needed.
Unfortunately, my camera's battery wasn't charged so i could only take a few pictures.
Some tips in disassembling and optimizing the AGM Sten:
1) Much easier to disassemble than the Viva
2) Disassemble the barrel assembly first. (It'l be easier to take out/install the gearbox)
3) The gearbox sports brass bushings on the bevel gear but nylon bushings on the spur and sector gears (standard size gearset) --change the nylon bushings to 6mm steel bushings
4) Change the Type0 (closed) cylinder to a Type2 (MP5/Sig552) cylinder - this will match your cylinder-to-barrel length ratio for efficient firing.
5) Change the plastic spring guide (ver.3) with a metal spring guide with bearings
6) I opted to keep the spring stock to preserve the gearbox.
Now to the Hop assembly:
In stock form, the hop arm has a very limited travel arc. This is because part of the hop assembly is blocking the way.
You will need to file off the part of the hop underneath the hop arm:
Also, you will need to round off the corners of the hop arm itself:
For some reason, i couldn't find a hop nub. What i found under the hop arm was a plain old tiny spring, acting as the hop nub. I replaced this with a piece of rubber insulation from a wire ( i forget what gauge).
After these simple mods, my hop is now adjustable:
Hop off:
Hop on:
Hop on using the grub screw:
Thanks for posting I may have a go some time 
Free speech is expensive these days!
Tested this on the field last sunday. I was getting 380-390fps with the stock spring. This is probably due to the teflon sealing of the cylinder head and hop-barrel junction. I was getting greatly improved range too thanks to the hop mod. It was a little tricky to adjust though, because it was really sensitive.
