I've had the glitch problem on an open class glider (120" span) with a 4 servo wing. I found from other glider guiders that it was pretty common to have this with long extensions. Twisting helps but mostly they depend on ferite terroidal coils or "lifesavers" (shaped like the candy). Just wrap your wire in and around it about 3 turns near the rcx and your are good to go. Multiplex sells them and they might be more effective than buffered amps. Some have claimed 6 volts systems are less prone too. I'm right with you and was asking what to do on my 27% the other day. Gassers said "PCM". I think I'll do both PCM and coils.
Jack