Navajo shakes and Jiggles, another look

I have read the earlier posts regarding the shakes and changing the CG settings. I always load out the aircraft with my weight 196 as pilot, my wife 124 copilot seat and either our baggage, about 71 in the rear or some guests in the rear seats and additional baggage.Where I notice the jiggles is after climbing out at 120 indicated, when you level off and accelerate through 140 or 145, after that indicated airspeed the sim smoothes out. When viewed from the outside the elevator appears to be shaking. Is there a way to dampen this movement? My thought is something in the configuration makes for an elevator flutter to occur as these airspeeds are passed through.Zane