Peter
I'm glad to see that you have upheld the "evenly balanced" nature of this forum and only quoted an "average" machine (VBG). These things also seem to be badly affected by their position on earth and of course by the awful weather this side of the pond. Must be too wet for them (VVBG) over here. Sorry Peter couldn't resist.
I also can't imagine that it is good practice and in my ill informed state would worry about the difference between the static loading of the bearings with 3/4 ton on a line contact and the normal dynamic loads that the spindle bearings were actually designed for. While I'm happy to accept the 7.5 ton load on a 1/4" bolt and have often risked my life in those cars that Chapman created to prove it. We are not looking at total failure as the only cause of likely damage here. All we need is some deformation of the bearing track or roller surface to create enough of a problem to reduce the life or performance of the machine. A couple of other things would concern me, the 3/4 ton load will in fact be greater to overcome the inertia needed to lift the machine and I've worked with many crane operators who are quite capable of breaking things by snatching fairly small loads. All these worries without getting as far as the potential bending loads on the spindle which again will react differently than when loaded statically rather than dynamically.
Merely voicing my ill educated concerns as I'm certainly not qualified to provide real answers, I'll leave that to the PhD brigade. I suppose I would ask why take the risk (however small) of causing damage by lifting this way when there is no risk to the machine whatsoever if you use the manufacturers recommended solution. Is that slide rules I can hear clacking, oh no silly me it's calculators these days.
Best regards
Keith