It's been about a year and 15K miles now and the B Pillar leather is still in place. I used the 3M trim adhesive, but not the spray on.
Once the leather is carefull removed from the aluminum plate both parts need to be cleaned of the old adhesive. Once clean and dry I used a scrap piece of cardboard to spread a thin coat of adhesive. I made sure there was good coverage around the seatbelt adjuster opening and along the edges. Work in sections, doing the center face first, then the sides. Once it was glued up I left it sit unmolested for a couple days to fully cure.
If you only want to try to secure around the opening you could try to gently lift and clean the aluminum, then apply the adhesive without removing the leather completely. work on side of the opening at a time, let the glue tack up and work the leather tight then clamp and let sit. After an hour or so work the opposing side, then repeat for the other two sides.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.