I'm not sure, because I don't have a Juki, but I am thinking you might want to order a hopping foot:
http://www.finishingtouchesquiltings...s/show/3134568
Before ordering, I would email the owner with your problem and ask if this foot is the solution.
On my Voyager, it's possible to adjust how high the presser foot rides by taking off the cover and making an internal adjustment. However, I suspect you do not have this option with the Juki.
If you haven't already, you may want to join the homequiltingsystems group at groups.yahoo.com . It is a very large, active and diverse group of frame quilters who may have a specific answer for this problem (as there is sure to be someone on that list who has found a solution).