Steve, When you set the forms 1 at a time they will be  in alignment with one another, if you follow the measurements in accordance with the first 1 being just 6" off the bow you may not get them at the exact measurement they are suppose to be at, some of mine were an inch or so off, the aft molds are spot on as far as placement, when you hot glue them in they will stay in place when you  squeeze the next one in, make sure you check your fairness after every one is placed, to make sure they dont cause a squareness to the side walls,this is why I adjusted mine from the actual measurements. Also pay attention to the 7.5 and the 8.5 molds, they flank the permanent bulkhead, they will make the bulkhead seem like it is pulling the sides in at the bulkhead point, if you dont get those measurments right, other than those points, the moldings will be fine,and if you put the crown of the molds at the top of the side walls, when you lay your test strip across them, your duck will be very fair, good luck at be sure to post some pics once your under way....happy building.... Ocean