http://www.arms-cool.net/forum/thread-61765-1-1.html
Some overview on how compatible it is with WA. Chinese reader helps...
Summary:
-WA hop-up/outer barrel works on the VFC(if needed some minor work)(parts used, 5KU barrel extention, 5KU hop-up, Ino steel outer barrel)
-WA spec BC needs major modification, the valve-reset/cut-off lever is on the opposite side of the WA design, needs a new groove cut in to function properly(not sure how RA-T did theirs).
-WA spec bolt works, if not needed some mod(he tested 3, Element PPS nozzle, Pro&T(needs mod), and Ino 2010 aluminum(needs mod).
-PGC mag needs the bolt lock-back mech and the valve lock removed, needs some shimming in the mag well(loose), and the gun needs to be cocked(or shave down the valve) before it can be inserted. Use PGC 0.45 spec rubber.
-He broke the buffer retainer(swapped with Ino one for replacement), and broke the bolt carrier(replaced with a modded WA spec one, by cuting a new groove)
-He mentioned the gun use a lot of gas, semi-fire is ok, full auto the propane spews out of the gun very easily. Part of the mod he did on the WA bolt was to make his groove shorter than the stock VFC to cut off the gas earlier.