I'm working on specing/quoting for a job and I'm trying to decide the best way to make the mould. As usual, it has to be as cheap as possible. The job is to make 4-6 (maybe more later) simple rectangle crates - 5 sided, open top (or to be closed just with a bit of ply or flat sheet) gel coat finish on the outside. The finish doesn't have to be great as they're only for floating a pontoon on, I just need enough of a finish to ensure easy releases.