I have a well Mb03 with a AA Teflon cylinder. No real fitment issues (no sanding and such. The biggest mod to get it to work was drilling out the stock bolt handle to get it to fit. I did do this mod to smooth bolt pull and take out cylinder to receiver play https://www.airsoftsniperforum.com/...linder-guide-rings-easiest-cheap-diy-fix.html
It works great. The AA hop-up chamber fits decent too. I did add like 0.005" shim in there as well to take out the clearance and make the hopup chamber a tight fit in the barrel.
Maybe I just got lucky but I have not had any real problems with my Mb03 and action army parts. Now an "TM-spec" piston will not fit in the stock well cylinder which I sure you already know and why you want the AA cylinder (which is the reason I got mine).
Just curious to what you reason is for suggesting a AA outer barrel Silicon?