Put three more flights on it last night. I have managed to stop the tail flutter by stiffening up the fuselage just in front of the stab. Some observations:
1) it doesnt fly tail heavy, but it climbs slightly in knife edge.
2) the rudder is incredibly sensitive at speed, so much that a knife edge looop is about 20 feet in diameter.
3) I've got 50% mix in the aileron and it still rolls slightly on rudder application.
4) I've got the dual rates down to 25% on rudder, but of course it won't stall turn with that, so to fly the schedule, I'll have to go back and forth between rates (or mix it into the throttle).
5) except for the rudder, it flies exactly like a Dr J. The extra wing area really doesn't slow it down for landings like I thought it would. Evidently this is a very low drag configuration.
6) Oh yeah, ailerons are also extremely powerfull. I may disconnect the bottom wing ailerons and just have them come on for the rudder mix.