I replaced the chinese bolts on my Dax Friction Drive, where the u-bracket mounts to the frame, and added a couple extra nuts to lock the bolts in place where they first go through a bracket. It made it WAY more stable.
Then I added a foam air filter into my rubber air boot, made from cutting a disc out of a Lawnboy $5 foam air filter (made 2). I started and ran it, seemed to stay put ok and ran fine.
$1.30 instead of $5, here.