Interesting... Though always remember to account for singular ascending letters like 'I' as being usually three times narrower than other characters and sometimes four times proportionally smaller than letters like W,M,K, etc, this can throw out the centering of the text line. I learnt in West Germany so point and MM were the terminology rather than Inches.
How do you design your fonts? Have you just practiced lettering so much that you imagine your letter designs and just estimate the measurements to match your vision? It seems so free-style.