I knew I should have gone metric all those years ago!
We may be at cross purposes, but I assumed the aim was to establish the models length at a scale of 1/16.
Yes those little (') in my world are feet or ft, while their cousins (") are inches or in. I never realised this was not a universal method of indicating feet and inches. As you are still championing the imperial system, you may continue however you see fit

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Using pen and paper, and having been dealing with customers all day, I have roughly calculated a 252 ft sub, scaled down to 1/16, at roughly 16 ft long.. big.
Took me so long I got beaten to the punch