hello Geoff, met you at dalby yesterday, now I know why you knew your weights. there is another which gets seriously overlooked - c of g . one can be under mtofw but get into trouble real fast if c of g is out. had a personal experience 30 yrs ago, was taking seed out to other farm once in our Cessna . started loading seed and at breakfast decided I had enough for job, but had been loading to rear in expectation of adding more up front for correct c of g yet still below mtofwt. had get to jobitus, and didn't redo c of g calculation, well flight was interesting, great short takeoff an climb ,but didn't trim too well for cruise, hmm, brainwave did calc in flight ,hmm oh dear , got there, landed REAL carefull, got out an tail hit the dirt in front of megaboss (dad , who also is a pilot) , who then rightly gave me an earful about balance an weights, have not done it since, so tis easy to think yeah I'm below gross BUT don't forget c of g whatever the payload weight.