I cut the metal connector off the stock seatbelt, and found that the stock loop would fit perfectly over a ½” x 1” bar of metal, so I fashioned a bar that I could use as a transition between the stock seat mechanism and the harness.
I then connected the stock seatbelt mechanism to the previously-made seatbelt bar and permanently mounted it up by against the roof. An added benefit to this design is it gives extra support to that roof area, which is made from thin fiberglass. It now feels much more solid when pushing against that area from the outside, and should even contribute to a solid feel of the plane in flight.
Creating brackets between the stock seatbeat and the harness
Connecting the stock seatbelt mechanisms to the bar I made
