More on the John Austin seat belt mod...so the brackets are all done and I had my friend Al, do the welding for me. Essentially I had already drawn center lines down the long tube before making the cuts, after careful measurements...accounting for the thickness of the .070 end piece my measurements were 997MM on the short side and 1008MM on the long side. I did one side at a time and cut short of the line. I ended up being happy with my first slice (Dewalt Grinder w 1/8" blade)...so adjusted the second cut accordingly to hgit the measurements.
I cut the end pieces square and oversized, based on a pic I saw on the Zenith forums buy STOL builder David Beaullieu...really good idea because a lot easier to weld the oversize piece and then grind down to size. I drew cross center lines on the oversized squares and drilled a 3/8" hole with a unibit...nice and round. Then I had Al, weld the nuts on the inside of the end pieces. We held them in place with a 3/8 bolt prior to welding. So...used 3/18 by 16 bolts/nuts...Grade 8.
Then I placed the end pieces on the tube, eyeballing those centerlines against the center lines of the tube...and taped them on two sides. Then Al, did a spot weld (TIG) on the two untaped sides, removed the tape and finished it up. Finished the edges on the scotchbrite wheel and did a trial fit in the rear fuselage. The four point seat belts will drape over the steel tube...a great system but about a 4 lb weight penalty.
