Wow, looks like you're doing a beautiful job, especially if you've never done this kind of stuff before. As far as checking the bottom, it's much easier to flip the boat over where you can kind of map out the bottom. You work with a long straight edge, (minimum 4', longer is better), about 48"-60" from in front of the intake to the back, and from chine to chine. Measure the clearance between the straight edge and the bottom. It depends on what you want the boat to do as to how crazy you get straightening the bottom. If you're 3/16"ish or less, personally I wouldn't mess with it. If you decide to flip it, put up some picks so we can see what you have. Keep up the good work.