Some people have had luck with balancing the wheels, seems that an out of balance wheel can help “excite” the shimmy. Also others have added leas shot mixed with epoxy to the front inside the wheel pants, seems to shift the CG of the pant forward and may help. Other than that, as you’ve discovered, adding too much air can cause a shimmy. I don’t feel the risk of damage to a tube is a problem down to 30psi with proper landing techniques, don’t side load the landing my landing sideways, proper cross wind technique, ect.. I start at 40psi and if they still shimmy, try 35, then 32..