This is the core issue to me. I cannot understand the logic of weighing one with and one without. Makes no sense to me. For those that say "FAI does it that way", well consider that FAI weighs helicopters in F3C with fuel or batteries and they have a 6.5kg limit. So the 5kg battery but no fuel thing in F3A is not some sort of sacrosanct thing embedded in the genes of FAI. The one observation above seems most spot on "We do it that way because that is the way we have always done it".