I would caution anyone using someone else's W&B calculator to check it thoroughly before trusting it.
For example, on the RV-8 W&B program linked in the quoted post, I noticed a few things right off the bat after a quick cursory look.
1) It written for RV-8s with the "Dash-One" wing, which have a 1600 pound aerobatic GW. Aerobatic GW for RV-8s with the Non-"Dash-One" wing is 1550 pounds .
2) Each baggage area (Rear Floor, Rear Shelf, and Forward Baggage area) have their own weight limits (50, 25, and 50 pounds, respectively).
3) The RV-8 is stressed for Utility Category load factor limits between the Aerobatic gross weight (1550 or 1600 pounds, depending on the wing) and the Maximum gross weight (1800 pounds). The linked W&B calculator does not reflect this properly.
There may be other inaccuracies as well.