I did these last weekend. Everything worked out, in the end, but I had to make my own spacers for the existing belts (none were included in the harness packages).
Also, I don't know what type of X'acto knife they were talking about in the instructions, but none of the five (5) or six (6) that I have is worth a damn at cutting fiberglass! I resorted to holesaws, a nibbler, and ultimately, files to make the cut outs in the rear trim panel.
See here: deleted, so edited entry
Fortunately, I had some leftover Simpson hdwr on hand:
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I had to make these; trial and error, to get the right OAL, so the seat could be bolted back in:
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Refitting the belts, so the hdwr would nest in minimum space:
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Layout for harness slots (take your time & the results will be worth the trouble):
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Right side spacers:
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Test fitting:
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