Hi guys, there is manual for our seatbelts, which we´ve presented here: https://aeroscale.kitmaker.net/forums/165825&page=1#1393193



Enjoy.

Can I, please, point out (which means that I'll probably be accused of raining on the parade) that it is not just a "late," but a post-war harness, as far as the Spitfire is concerned. So far, the only aircraft, that I've found, to fly with that harness, during the war, were Tempests.
On the Spitfire, it was known as the "QS," not just "Q." The only Spitfires, which flew during the war, with that style, were the low-back XVIs (all) and XIVs (some,) but they differed slightly, since they were bolted directly to the head armour, and didn't go through the slot (largely because there wasn't one) because the fuel tank got in the way. That harness was the "QL." Also, the leg straps were moved back, and bolted directly onto the corners of the seat, which meant that they became hip, rather than thigh, straps.
Edgar