You might want to check that the forms are symmetrical by tracing half of one onto a sheet of paper and then flipping the paper to see if it matches the other side of the form. Assuming the forms are cut correctly then you should be able to just pull your gunwlae pieces down to the forms and hold them there with clamps or temporary screws. Scarfing for the gunwale pieces might be easiest if yo do this a day or two before you try to install the gunwales. Working with one long piece is going to work better than trying to join two pieces on the forms.

Can you post a picture of the problem you are having?

PGJ