Richard,

In theory the filler on top of the glass would be easier to sand without damaging the existing balsa wood. In my case,however, I cover all the balsa with two coats of urethane clear, sand it with 180 grit sand paper, fill any imperfections, sand the filler smooth,and then glass over the filler. But that is just how I do it. If I am really concerned about weight I skip the glass all together. In fact, I plan on foregoing the glassing process on my second Simla build.

As a side note, the Taurus I am building comes in under 5 lbs with full gear and no covering on the wing and no paint. That includes dual servos for the ailerons, an OS55 AX, and all necessary hardware. No contest balsa was used either.Done, it should come in at about 5.5 lbs. I am using two coats of clear over the entire airframe followed by 180 grit sanding, then two coats of urethane primer sanded with 320 grit sand paper, and then color coats and two coats of urethane clear. After curing 1500 and 2000 grit wet sanding followed by buffing with 3M finessit compounds.

Bill