it's just "simple" data isn't it ?
you may get into trouble if you're changing payload and installed equipment, if you're trying to compare.
if commercial you need to consider partial payloads and people moving around the cabin, some call this the "potato" diagram.
You will need to be clear about what is accounted for where (under which heading) ...
Basic empty weight is a very basic airplane, often without an interior
Minimum flight weight has the minimum (duh!) added, like flight crew and unusable fuel and oil.
Operational empty weight would add the interior (including seats) and more crew and fuel reserves.
Max Zero Fuel weight (with is a type restriction) adds so much payload
Max take-off weight adds fuel
You need these weight distributions before you can calc mass moments.
You're modifying an existing plane ? you should be able to get the mass distributions for the unmodified plane and then calc the mass moment, and then your modified plane's masses and then mass moments.
Some more clues as to what you're doing (and why) would help.
another day in paradise, or is paradise one day closer ?
