I'm not relying on my rotted stringers to give me the measurements I need in my Chap. No two boats were built the same IMO. I'm using some string line, (and helpers), laid from side to side anchored to where deck height should be. Using a tape measure I can measure points along the stringer, moving from stern to bow, (from stringline to hull), every few inches to get stringer dimensions. I will record these measurements every 2" the length of the stringer or bulkhead. I really don't think that any 2 stringers are cut the same. I think this is a pretty accurate way of doing it without wasting much material.