Right at the outset of building we came across a few errors on the plans which caused us to wonder what was correct and what wasn't. We checked and double checked as we went along but perhaps it was our inexperience in boat building that was part of the problem or else our ability to read plans or a bit of both.
However, we needed to be re-assured without running to the JWforum every 5 minutes or endlessly e mailing John. There were other little things too. For example - when measuring distances say, between frames - was it the aft face, the forward face or the mid point ? Did the frame dimensions allow for bevels or were they the finished maximum size? Perhaps it didn't matter - a 'Backyard Boat Builder' ought to just get on with it.
Our real difficulties were the the centreboard fitting the centreboard case, the position of the yawl mast step and the exact position of the 'notch' in the stem girder. The last straw was when we had to cut off about 100mm off the centreboard to make it fit the already completed case.
Fortunately my brother in law Jeff took the plans away and put much of it on autocad for our personal benefit. He spent hours and hours doing it but what a difference! We could see the exact dimensions of every part and felt very reassured. It would have been good to have started with his drawings.