I am using aluminum stringers (screen material) on my plane. I pretty much just eyeballed the shape that I wanted and clamped the first stinger in place. I started with the middle stringer and worked my way out from there.

I clamped a piece of wood across the plane level with the marks that designate the height of the stringers. I then place an aluminum bar over the wood. I used this tool to find the angle between the two.

I then bent the steel angle (same stuff I used for the formers) to the same angle found in the previous step. Next was to file one end to fit the longeron and then mark it where outer edge of the stringer crossed it. I then trimmed the piece about 1/8" short of the outer edge of the stringer.

Here I am clamping the standoff into position for tack welding.

I used this piece of aluminum bar to make sure all of the boards were level. I would do half of the standoffs down both sides and then move the other boards over to the uprights that hadn't been complete and do the others. That kept it from getting too cluttered with a bunch of boards and clamps. It is also easier to align the second set of standoffs since you can use a stringer or the aluminum bar across the ones you have already done to get the alignment.

Here half of the standoffs for one stringer are done (tack welded). After I did this one I decided to wait to drill the holes in the others until all of the standoffs were done in for each stringer.

Jump way ahead and this is what it looks like after they are all done. The bottom stringers aren't done yet.

This kind of shows the shape my fuselage will have once the cloth is on. In all I think there are 70 standoffs to hold these stringers on.