Simon, I recommend to move the cg farther aft, and try testing lateral CG, I'm not using any type of mixes on mine. Here is a few vids of mine, no wingrock at all, maybe you need less or more elevator throw???

http://www.aerofun3d.com/videos/fgvcglow_aerofundan.wmv
http://www.aerofun3d.com/videos/BB1.wmv
http://www.aerofun3d.com/videos/skycambbp.wmv