Axle housings, for example, often have welded on brackets sticking out of them, that make a 6" diameter part into a 12" diameter part.
Chuck
That they do. And that means imbalance.
Massive old Niles - War One era - and Lodge & Shipley, War Two or inter-war production - soldiered on into the 1970's and longer for Mining and Rail job/repair shop use partly because HEAVILY imbalanced parts had to be handled more often than not. And without shaking the lathe like a biscuit-eating hound dog s*****g chicken bones.
You don't need the latest and best, 12 feet of bed, nor 6 tons or better of Iron for what your stated use involves.
You WOULD be better-served with, for example, a veteran Hendey, raised if need be, that at least began life with a wide bed and
serious rations of good Iron in all the right places.
An "as-issued" Hendey tie-bar looks like a larger lathe that had been LOWERED, rather than raised, and basically that is what it was to get great stability and long wearing bed/carriage.
Raising one - and folks can do this themselves - just puts it back into the range of a "normal" larger lathe, but even so - an industrial, not hobby one.
An overly tall SB doesn't really even make a good mount for spinning large Aluminium pot-lids.