I think I have a pretty good handle on the process of spiling and installing frames and stringers, but it occurs to me that I don't know the preferred technique for leveling the top of them prior to setting the floor on them. I have built, restored, and repaired wooden boats for 25 years and I can come up with something, but I imagine there is probably a more straightforward process than what I'm thinking. How do you set the tops of floors & stringers?