Thanks a lot for the help guys. This is one of those topics that I could google all day and not find an answer to. After an excessive balsa dust in the home fiasco this weekend (sigh) I was hoping for a solution that didn't involve sandpaper but I picked up a 4-foot 1-inch square aluminum tube, spray tacked some 150 grit paper on one side, clamped it to my bench and used some smooth foam board to raise the balsa a bit and make it easier to slide back and forth. Works perfect and stores away nicely. The only improvement would be to build a grip to hold the balsa down firmly as documented in the airfieldmodels link above.

Gap-free sheeting finally. Thanks again!