Lee, the levelling bar method works fine, and is easy enough to set up if you remember a few critical considerrations.

Carefully measure the width of the root rib, at the spar cutout, and the tip rib, again at the spar cutout. we want the width of the rib to its' outer edge, not to the bottom of the spar cutout.

Figure 1/2 the difference between the two measurements, and that's the hieght of your shim at the tip. This will take care of the wing taper difference between the root and the tip.

Use two straight 1/2" square pieces of hard balsa as your levelling bars. These need to be reasonably straight in all directions.

Find the spot, towards the trailing edge,  where this 1/2" sq. bar holds the rib absolutly level with the work surface. Place a mark on the rib where the bar touches the rib when it's level and supported by the bar.

Likewise, find the spot on the tip rib where the same thing is happening.

Align your bar to these two marks and you have set up your levelling bar.

This only works accuratley with a single, constant taper. It won't work withan elyptical taper.

You're going to want to support that bottom spar to hold it straight and true. I build on glass and glue little blocks of balsa between ribs then pin the spar to the little blocks.

BTW: Lee, I like using the leveling bar system when building from laser cut ribs and such!

Frank and Bill I totally agree with the glass top, I didn't realize how much of an improvement it made until I got one. My small building area is a desk the original owner built in a closet inset. My house is all steel frame construction on a concrete slab and every wall is straight and true. He built it using the walls as bracing and used a 1" thick top covered in counter top material. The top is perfectly level in all dimensions, so I put dry wall on top and 1/4" glass on top of that. The only draw back is I can only get up to a 48" wing built on it, but at least there straight and the leveling bar or block system works fine in this area. Thanks for all the tips everyone.

Thats what I use to do when I built RC gliders. Up to 118" wing span.