Ideally you would like a seat that has openings for the shoulder belts to rest on top of your shoulder.
Not resting on top of the high back seat...
If you run the shoulder belt over the top of the seat the shoulder belt could slide off the side.
Also you might get a false tighten if you are pulling the houlder harness on the top of the seat instead of having the belt wrapped around the top of your shoulder.
Also the seat should have a hole between your legs for the sub belt.
Without a sub belt the shoulder harness with pull the lap belt up too high on your torso.
The sub belt locates the lap belt,,, after those two are tight then you tighten the shoulder belts.
Also on the sub belt I prefer the 5 point style, it stays mostly out of the way towards the front of the seat base.
The 6 point belts attach the sub belt to the lap belt mounts...problem is then you are always sitting on two sub belts...
just a big hassle I thought.
If you don't have a roll bar for your shoulder belts..
some Porsche racers lacking a roll bar use a cross bar that is used for shoulder belt mounting.
This would require some fabrication for a VW as I dont know of a crossbar seat belt kit for VWs.
The belts you have seen incorrectly installed may never go to the track or have never have had to pass a safety tech.
I got dinged once b/c I forgot to cotter pin/safety wire my hook in belts...
fixed it at the track but took some time to remove the seat to cotter pin the belt hardware.
Yes you need to have your belts correctly installed...your first drawing is not correct.
Dont short cut safety and dont use vintage out of date seat belts or seats.
Two thoughts:
Why doesn't he have arm restraints on in an open cockpit car, and...
Why are his shoulder belts mounted higher than his shoulders...
http://www.youtube.com/v/e-9XSOM5eIo