That is a great reference source for the intent of the seat-type design at the very least, even if it is contemporary, it should help, thank you!
Here are (some) of the references I've used, although this discussion thread has encouraged me to rethink my model of it.
Today I also found another, somewhat clearer line drawing of the seat:
Info is sparse on this design, with several grainy photos from the era that do not really help with specifics. It also makes it a bit confusing as the RAAF uses a slightly different design, along with the Luftwaffe and the USAF.
The best 'in situ' photos I've found:
Thank you both for your thoughts on this. I think I will redesign the strap portions at the very least.
Tirick