Hi,
I'm not a loadie or anything related to aviation, just a simple-minded physicist, so take this with a grain of salt... I'd say you're absolutely right with your 667kg/m^2 - that's the pressure excerted onto the floor in the areas of the spreaders (and in between there's no pressure at all).
Now how best to argue your case? Instead of having spreaders (the name says it all, I guess) consider the case were you had your load on legs with 1x1cm sizes at the extrem edges of were the spreaders are now. Would anyone still argue that the load would be 444kg/m^2, just because that's the area enclosed by the supporting four legs? I guess anyone would see immediately that each of the 4 legs would have to support about 500kg, resulting (with the above assumptiong of a 1x1cm profile) in a pressure of 5000t/m^2 below the legs. Making the area of the legs larger reduces the load, but only when the whole 3x1.5m^2 area is loaded equally you get down to 444kg/m^2.
Of course, if you can show that the spreaders are on top of load bearing structures that can take a lot more things are different, but then you don't talk about load distributions and any "maximum loads" don't make sense anymore.
Last edited by jtt; 6th Mar 2014 at 22:16.