Maybe you've had more advise here than you need but here's my two cents. With my Georgian Bay I tried a host of external things like strap clamps and tape clamps. They didn't apply enough pressure inside for the narrow half nor outside for the wide half. The problem was a little of both. Finally a friend came by and calmly suggested that both halves fit fine when they were on the molds? I forced the two molds on either end of the cockpit back in place and presto I had the sides aligned properly which also aligned the two halves for length and solved all my problems. I did have to cut out the molds later but that was no problem. I love this forum. 3/4 of the responses attempt to tell you why theoretically it happened instead of what you should do now to solve it.
Best of luck with this. Stan