i have some seats coming in from a 1987 formula boat. Not the bucket seats but the long bench pieces and sun bed sections.
The seat back and seats consist of separate pieces for each colour of vinyl. (really like the designer). However these pieces seem to have 1/4" foam sewn to them. There is a line of stitching by the staple line. Is this standard or just the way the last upholsterer did the work?
I've never re-done a Formula of that vintage. Typically it's foam-backed vinyl but that's '90's and later. Who knows what they were doing 30 years ago. But... I doubt it's original. Most likely just the way the last upholsterer preferred to do the work. It happens to be the way I do upholstery if I can't find the foam-backed in the right colors. I cut sew-foam and stitch around the perimeter of each vinyl piece before sewing the bits together.
June
I prefer to glue it. Its just my way any way that works.
You can get away without using foam, but the overall appearance is smoother if you do. It also hides imperfections on the old foam cushion that can telegraph through the vinyl.