ah understand
that wobble at about 30 seems to be the nature of some beasts... with 3 wheels rather trike or sidecar... no explanation why that is....
i dont believe the rear psi will make much difference...at least not on any that ive build
a little lower in the front might... but if i remember .. low enough to help.. the tire is way lo an would over heat..the front
i have had one sidecar and one trike i couldnt get rid of the wobble no matter what i did .. and gave up... got the best of me (i hate that)
this is what i used...
https://www.jbugs.com
seach pn 113425021 or 113425021J
there are several version i find these work well
certainly more place even an auto supply would have them i ask for one for a super beetle 71-74 i just did a google searh to find u a photo
you need a heim joint 3/8 i think for one end
it should be as close to 90 degrees from the stem so it doent wear out the rubber bushing..
and it can be quit a pain to get it in the right spot so you are using the full travel of the damper
this was the side care obviously not a sliding front end but still a pain to get in the right place
if you can afford it at some point go with the trees you will wish u did it sooner... steering is so easy