Bent and cut the big flanges of the exterior steps to get a nice flush fit to the fuse sides. I drilled an exact 1.5" hole for the step tube which fit nicely. But it turns out the weld bead of this tube to the flange needs a 1.75" hole! Used the Dremel to cut about 1/8" from the edge of the hole. Also had to take about 3/16" off the end of the step tube to get a good flush fit without the inner baggage floor rib interfering. Cut the flanges with a Dremel thin cut metal wheel (same thing used on the tubing and the now-1.75" hole in the fuselage side. Laid out the holes on the flange and drilled, then match-drilled to fuse side. Struck a line for the rivets that must go thru the step flange to F-724, and match drilled in (clecoed) assembly. Fit the UHMW blocks to the end of the step tubes and drilled them to the inboard ribs.
Last step was angle-drill thru the previously drilled blocks through the step tube for the cross bolt. The orientation of the blocks on the rib and the steps on the fuse sides were AOK and locked in with clecos, so the cross-bolt holes are in the right place. There is a bit of a gap between the step flange and the F-970 skin aft and down where conformance to the curve isn't perfect. This gap is evidently present on several aircraft on VAF. There's no structural rivets here, so it will be filled with something lite weight after the steps are riveted on.
Finished by clecoing the seat and floor pans into the fuse--ready to rivet F-970!