Shoulder Harness Bracket Size and advise on 4 point set up

The seat belt set up needs to be fixed. My aim is 4 point, may be 3  point set up.

so far I have fiddled a standard 3 point into the Rocker-side-space as original (although only 2 points original =  non- adequate for me), by adding some sheet SS metal to get the right distance and angel inside the rocker space. Belt system works but the set up is not nice. I would need to flip the two cover Steel plates left to right and right to left and then have some stich the belts fixture back in place, as I need to un-sew it to fit in the original slit. Will not do that.

Also the mounting for 3 point on the firewall I do not like as it makes it, as I guess, harder to open the firewall up for engine access..Correct???)

So think I would go for 4 points bels set up via Shoulder harness. Hence my questions for USERS of this set up within the Team:

1) can you please comment on the setup, is it workable or too cumbersome to get the belt set and straightened?    I do not drive the car to Win Dixi or Albertsson , her ALDI etc..for a beer (case)      

2) can someone please measure the WIDTH and THICKNESS of the Shoulder Harness Bracket (can build it myself as US import is terribly expensive at the end.., better get several cases of beer instead..via my cargo BMW 540V8 Sedan)

3) Europeans ..Which 4 point belt system with EU approval do you use PLEASE !!!

please comment, any suggestions appreciated.

Matthias ..... nice cat it is..
Original Post