After having my ICS grease gun now for a while it has annoyed me slightly that ICS havent given any furthur support apart from bringing out spare high cap mags. (That and the ICS Garand was a little sub par) So I have decided to do a project with the 4 High Caps that I own.
What I want and What I already know:
Convert Highcaps to Mids or lows.
Not destroy any of the Highcap parts so I can change them back if I go to open days or wish to sell on the gun in the future.
Ares Mags will not fit. As have tried and tested.
I wont a cheap source of mags to use as already have spent almost £25 a mag on the High cap mags themselves.
So I was looking at some of my current WW2 stock and found a mag which had the feeding hole aligned so close to the original it was just meant to be!
MP40 / Sten Mags! The plastic King Arms mags are just the ticket as they are cheap and the plastic is easy to work with. Did 3 in under an hour and the feed with no issues at all!
Pics coming soon.
Will not bother finishing the guide off now as the lowcaps are now avaliable. 
http://shop.ehobbyasia.com/ics-m3-low-cap-spare-magazine-for-ics-200-aeg.html
Stu