I have been procrastinating on making the seat belt/shoulder harness cutouts for some time now. Like most things, thinking about doing it is actually worse than actually doing it. I placed my seatbelt cutouts differently than most folks (best I can tell).
Most I have seen come up through the "floor" of the pilot's collective. On of the things that would have made this difficult is that I had a folded and riveted seam there. It would have looked pretty bad to cut into it. I had to do that for the Collective hole. You cannot really see it, but it does not look real good.
The seat belt is routed around the tubes under the seat where there are no sharp edges. Where you see the cutout in the photo is directly under the seat support tube. The belt can rub on the tube but not the sheet metal. I will however put anti chafe edging around the hole.
I went a little more conventional with the center belts. I made the holes big enough so that the belts did not touch the edges.
To locate the shoulder belt holes I installed the "headboard" then marked the back side at the base of the attachement tab. You can see the tab in photo 1.
I made the cutouts the same way. I drilled holes at each end with a step drill. I then used a cutoff wheel in a Dremel handpiece to cut away the metal between the holes. I was shocked at how well the Dremel worked. It cut the aluminium like butter. I wish I had tried it quite a while ago.
