I have just try to install a new small ecu for my ptw clone, ctw m4a1 in order to use magpul stock on it.
first, remove parts like grip,grip end, old ecu.....
unscrew the stock tube and size compared with ecu mosfet unit and 11.1 firefox battery
remove old ecu and install new ecu
also a new elc-001, software programmable full atuo and 3 burst
almost finish...battery inside..
finally, a magpul stock on my ctw :cheers::cheers: