My head gets firmly applied to the desk when I hear, and read this sort of thing. geoff, Im sure you have a great attitude already towards this sort of thing, but just to make doubly sure you are not lead astray by your FTF and the people you have been talking to.
MTOW is a very real number that ALL pilots in ALL aircraft should not only be aware of, but abide by STRICTLY!!!!
Its not something to be messed with, if for NO other reason, in the event you have a prang you can kiss your insurance goodbye if you are over weight.
Secondly, CASA can and will ramp you, and if you answer the q, like the guys in your first post, well then expect a nice letter from them which starts with the line " We have made recommendation to the RAA that your privileges as PIC be suspended"
Thirdly, if you fly + MTOW, you are essentially a test pilot, as the aeroplane's performance is now outside its design envelope. Sure, it may fly quite happily, but the way it behaves may vary quite significantly.
Further to this, the C of G is rated at MTOW with Pilot and Pax and BAGGAGE etc being UNDER MTOW (Useful load) so there is no garuntee's you are within the design CofG range (a very scary thing indeed)
Lastly, and probably the most significantly, if we are to hold the concept of "airmenship' with due regard, then knowingly flying outside a design limitation puts us on the bottom end of the 'airmen' scale IMHO, and if we are prepared to either bend this rule, or not care about it enough to even KNOW the numbers, then im afraid we are just accidents looking for a place to happen.