The plans for this kayak call for a 12'6" strong back and 10 inch spacing between the forms. I used half inch MDF for my forms, so my net size for spacers was 9 1/2 inches. However, this leaves me just about 7 inches for the final wedged spacer at the center. Clearly I've got something wrong, but I can't seem to pinpoint it. Is this situation and ringing a bell for anyone? I have got the penultimate forms on either and positioned flush with the end of the strong back. It occurred to me that these might need to be positioned just outside of the strong back, but that would only gained me 1 inch for the center spacer, and as I read the diagram on the plans, that wouldn't be right anyway. Thoughts?

Thanks,
Patrick