I took the plans, backed them with carbon paper, then traced over the outlines, centerline and baseline onto light cardboard. Then I cut out the cardboard and traced around it on to my wood forms. I can keep the cardboard against ever wanting to make a new set of forms. Each piece of cardboard is a half a form, but since it is an outline it has neither leftness nor rightness. As long as I align the centerline carefully when I flip the cardboard and match the keel line and the baseline, my final forms are true.

I think it's important not to try and match too many reference lines when setting up forms like this. Get the centerline and the baseline accurate and, like Ross says, plan on doing a little fiddling on the strongback until your test strips lie fair.