Hi Paul,
Now you mentioned the water line I had another look at her on the water and yes I would agree with you she is quite high this would tend to make her a little unstable, I went by the plan for the boot topping and also looked at several photos of the battles and they all sat quite low in the water, so I based my boot top on them , and I was pleased with the result as she is very stable, here are the measurements you asked about I hope they help,
And no it doesn't sound daft to build a competition model, you go for it, most people could not achieve what you already have. Joe