This idea came to me on my morning walk, as do most ideas. I'm going to use the Bottom Doubler as an installation template and I think that the completed Center Spar can be used to install the Front Wing Uprights. Here is a picture to setup the thought process.

Using the existing Wing Attachment Uprights, some reference points can be established and it might be possible to drill the 5/16" spar bolt holes, A5 rivet holes through the web, and pre-drill the Front Wing Uprights 6ZU2-6 for the fuselage.

This is just a test setup, the old Wing Attachment Upright needs to be trimmed so it doesn't overlap the Top Doubler or Front Bottom angle. Clamp a straight edge to the original set of Wing Attachment Uprights, I'll use the bolts to ensure proper alignment. Obtw, I had to do some minor trimming on the rear Wing Attachment Upright.

In this example, 70 is the mark and represents the fuselage side skin. Not sure if this will work, but after clamping the Front Wing Upright I will drill and cleco the A5 holes into the web, then I can drill the 5/16" spar bolt hole. All of this can? be done on a workbench. Then I can pre-drill the fuselage holes, one at the bottom and one above the top of the spar, and drill the remaining out to the top. After drilling, draw a line between the top and bottom holes and drill, otherwise I'll have to use the right angle drill attachment. The other alternative is to drill a top and bottom hole in the Front Wing Upright, drill into the fuselage, connect the dots, set the pitch and drill.

Whatever path I take, I will add to Center Spar Upgrade - Final version. Guess it wasn't final ;-)