The seat runner effect is easy to ballpark without a spreadsheet.
Two heavy people could be about 20% of the aircraft weight. Moving 1/5th of the aircraft mass 5 inches moves the CofG 1 inch.
PS. This is an illustration. Obviously, there are some A/c types which do not weigh the same as 10 heavy people.
Last edited by 24Carrot; 14th November 2010 at 17:27.
Reason: CYA re types, etc