Well, new tires installed today ... I was coming down on balance, but want to ask here as many of RV.net guys know more than my 'little bit' about tires ... Will have installed balance again ... and see. If not, will have them put on a new set. Mfgr has a 30 day exchange if you don't like the tires - so will exercise that option if the installer can't settle the vibration.
I'm more worried it will increase if I jsut let it go and skip the 25 mph issue, but no matter, it still means something is amiss with these tires.
An aside: HA, our housing community has a 25 mph speed limit, so of course, we vibrate at 25 mph --- go figure.