So I'll apply glass/resin to the mold and a ways up on the weirs to build some flanges for the mold pieces to bolt together with. This thing has a coat of PVA that is drying for an afternoon layup.
I learned this trick of roughing out a complex curve from a guy who build a gas tank in a similar way on Bay Area Riders Forum. Reminiscent of differential calculus in a way, but there's nothing some old junk mail cardstock and a glue stick can't do
Once the patterns are made, I just transfer to some tougher card board and then cut out and seal with packing tape. Few minutes of hot glue gun action later et voila