Richard,
I built a lapstrake canoe called Charlotte, designed by Tom Hill. Tom Hill's method uses ribbands to define the shape of the strakes. In Tom Hill's method, you mark the shape of the next strake prior to glueing the previous one. This is how you go about it using Tom's method. However, when doing it like you are doing, I would say be careful not spile out a strake any further ahead than the next one to be hung unless you insert a small piece of the planking thickness at each station mold to represent the not-yet-hung strake prior to the one your are spiling. (Tom Hills method) It doesn't sound like that small thickness will make a difference but it will. What will happen is the strake will not fit properly and will have to "edge set" or forced into position once it comes time for that one to be fitted on the form. Of course if you cut the strake oversize then you will probably be ok. When I built Charlotte, I had very little waste by not cutting the strakes ovesize.