mass balancing will help a lot and I have my CG at about 150mm so I could take that back to 140mm with a little weight aft, should not take much to balance the very light elevator. I believe CPLR insisted on square trailing surfaces to get better control surface response even though it would make flutter more likely. I do think digital servos with their much better holding power stop flutter before it can start. At our local field we have had 4 ARTFs lose their elevators and or stabs. Two Seagull kits and 2 Flair kits all caused by flying fast and pulling up. Flutter is incredibly violent and powerful, the trick is to stop it starting in the first place, once it starts solid elevators are not going to help.