All,
I purchased an Experimental PA-12 and while posting here, found out the seatbelts were not ideally set up. I have been working on getting things right. This video shows the process I used to come up with seat belts. This may help the next person.
They look very nice.
I like an inertia reel arrangement myself, at least in my C180.
FWIW Cub Crafters sells inertia reel shoulder harness / lap belt kits in two different lengths for $459 each.