Rebuilding a bench seat

Use high grade/ high density marine grade foam.
I firmed mine up (buckets) with stainless steel aircraft safety wire by tying some of the springs together spreading the load better.:lol: after mine were done /I thought about using old chair/couch springs /drilling the seat frame for more springs.

https://www.bing.com/aclk?ld=e82nd-...=b210b36a310f1f82239cd7deb62de219&ntb=1&ntb=1

This might be an option..