Hey Peter, remember that most of the weight of the A5 scope moves anyway upon recoil, so the mass it has to hold is by far less than on any other mount. And as tiriaq mentioned, modern adhesive is far from what we were used to. He said he will do an experiment, and I'm really looking forward to his resuls!
Hey Bruce, another big advantage of the Whitehead mount is the simple fact that you can choose yourself where to drill the holes for the commerical bases, if you anyway do a reproduction. And if it were me, I'd fit it exactly parallel to the scope tube, and also zero it that it hits exactly the same offset than the scope from the barrel on target. This is just something you have to remember, but then gives the same offset on all distances.
Talking on the Australian SMLE mount you are of course fully correct. But I also like it for that reason, because that allows to spot fakes rather easy since nowadays gunsmiths are not used to such work.