Albervin, thank you.I made my new seat base from 7/16 marine ply after I found my 1949 seat base had delaminated!! I cut the new base very carefully and rounded all edges.I then liberally coated it with Penetrol wet on wet coats after I drilled the holes. I re-used my original Dunlopillo foam which overhangs the base by about 1/8". All metal parts were soda blasted and epoxy coated.
Think I'll go the same way but with 1/2" board.