The high speed noise is very common in the ASG29. The ASW 27 will also make the noise but needs to be at high altitude and high speed (like 17k at 105+knots.)

So sadly, I don't know of anyone who has cured this yet but maybe broadening the question to include ASW 27 pilots who fly regularly at high altitude will yield an answer.

In my own plane I've tried to seal air from getting into or out of the vertical fin via around the elevator and rudder joints. Not cured yet but I'll be at the Utah nationals next week so I'll be able to test out a couple of ideas.