Mark,
I installed my Ultra-Fabs the same way you did. The front of the rig feels very stable, but the rear still has a shimmy. So much so that you can watch a lamp shade on a table lamp wobble if someone is walking around. Tightening the attachment points just beyond "snug" and extending the jacks a tad more and resetting the struts seemed to help a little, but not completely. May need to reexamine the rear stabilizer jack system to see if there is some play that needs to be taken care of.