OneTrack
ISO 898-1.
http://itc.co.ir/wp-content/uploads/...98-1_2009E.pdf
Australia (and basically the whole non-US world) adopts UN ECE regulations which do not recognise SAE standards (the one exception I am aware of is dimensions for the SAE H-point dummy).
My point about seatbelt strength has, I think, been lost.
A chain is only as strong as the weakest link. Seatbelts are attached with (I think) 7/32 AN bolts attached to typically 1.0 mm steel brackets that are often pop riveted to the aluminium fuselage without reinforcement plates. I wouldn't like to guess the strength of the attach point, but it won't be good and is certainly not designed for forward moving crash loads. I suspect the manufacturers really intended them for in flight turbulence. Use whatever webbing you want. The failure point will be the attachment.
Frankly, the same argument probably works for seat rails. The seat rails are designed to have seat loads push down on them, not pull. While the seat rail looks good and chunky, its attachment may not be very strong in tension (ie pulling from load restraint belts).
How will you secure the same gear in the car driving to the airport?? Big chance it will be unsecured on the rear seat?? Sometimes we get carried away with aircraft.