Schizophrenic here, too:
When building very small models I usually weigh them as I build them, in grams.
Larger models I switch to ounces.
Materials density for foam sheets of different brands, covering paper, and other things I use to build with, I compiled a whole spreadsheet for my own use calculating grams per square inch.
I still think of wing area in relative terms of square inches. That's probably because I know how much wing area a great number of models have in square inches -- dating back 50 years, so by comparison, if building something new that mental database is useful. And the square inch is a useful size to keep model wing area in the hundreds, so mental arithmetic feels easier to me when calculating.
I do mental conversions of mm to inches on plans (for approximate size glomming) by multiplying by 4, and moving the decimal point over 2 places. That I can do in a second or two.
I still use sixty seconds in the minute, 60 minutes in the hour, and 24 hours in the day......
Having admitted all the above, I absolutely
do not want to defend the imperial system, or the metric system in one of those ten (or twelve!) to the 6th power online arguments about "which is better". I have many ancient Model Engineer magazines where metrication (or metrification) was fervently argued in reader mail, as well.
Me, I am quirky, and use whatever feels most comfortable, but wouldn't inflict that on another!
