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You'd really have to test that out. How flexible your shaft and tube are will matter.
I checked some manuals from redmax, to look at the exploded diagrams.
here's one
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They don't really list what bearins are there, which is probably none, but I'm guessing the shaft they use is sufficiently stiff to not need support at any place other than the ends. Their typical engine has a female spline shape cut into the clutch. Lining up bearings and shafts is a pain, so they're probably just supporting one side of their shaft at the engine which has a ball or roller bearing at the end, and then at their little gearbox thing that changes angles and holts the cutting blade/string or whatever the tool uses.
To them, the less the part count the better.