Hi Bri, It is amazing using the Claudio device , when you join 2 flat panels and get a nice curve shape to the result. I think what the guys at the lake are talking about with twist is inducing a shape into a flat sail by the tensions in the rigging, particularly the amount of lift of the mainsail boom. Still a bit of a black art to me .
Hope you have fun making your own sails. Start with flat panel ones to get used to the "how best to do it" bits, then progress. I bought myself a large cutting mat to cut the Mylar on and use that to fix the sails down with masking tape on when applying tape etc. Look forward to knowing how you get on.