How I Built My Fittings
This is certainly not rocket science, but here is how I built my center section wing attach fittings-
I took templates that I had made to the correct size, and copied them onto 90 LB card stock paper I had. It is thicker than simple copy paper and feels just a little more stout.
(1) I then cut them out and glued them to one inch wide .090 4130 steel I purchased from Aircraft Spruce. I used Elmer's glue stick from our office desk drawer.
(2) I then cut the ends relatively close with my vertically set Portaband metal cutting band saw
(3) I then ground them with my bench grinder.
(4) Hand sanding a bit with extra fine emery paper to take out any rough edges,
The pictures show the progressive steps.
I then primed with ZInc Phosphate primer.