I suspect that the centre tank issue is that the normal fuel usage specified incorporates consideration of wing bending.
It will only be when you are doing something non-standard with fuel loading that you need to worry about including centre/belly aux tank fuels in the ZFW.
Slice .... can we please keep it a bit nice ? I have no interest in your thoughts on any particular PPRuNe member but, in tech log, we like to keep things on a more rational plane ....