You're right that they are prefitted with MOSFET, but I'd like to have a programmable ETU (twiddly bits).
I'm running the 7.4v LiPo that Patrolbase (my local dealer) recommend, so that's not my main concern at the moment. I know Krytac specify the 11.1v but I'm getting 330fps on 0.2g out of the box, so I'm happy.
There is a video on YT of a person who shows off the Perun in this gun, so I assume it's possible. If nobody comes back to me with a homebrew solution, I will ring round some techs.