The thing to rember is length - strength goes down rapidly with an increase in length ; by the square of the length in fact. For example a 36" tube would support four times the load at 18" and only a quarter of the load at 72".
You don't seem to be getting many answers Jim. This could be because either not many structural engineers are both beekeepers and forum members, or because structural engineers don't give advice for free . . .
I suspect that failure in bending will happen long before collapse in compression. Your answers are more likely to be found in aviation structural literature and at a fairly high level. Why not ask a manufacturer who would be more likely to know such things than a structural engineer - who would consult the manufacturer or the mfr's literature to determine the answer.
There is strength in numbers of course and multiple tubes would support more weight as would shorter tubes. So stacking two short arrays of 700mm tubes would support more weight than one array of 1400mm. Think lattice mast bracing or pallet type construction where the tubes are attached to sheet material top and bottom.
If you were able to share with us your application, then you might get a better range of responses (to filter to your hear's content).
In compression, I would imagine that your specified tube would be good for a tonne, but would likely fail in bending quite quickly if it was on it's ownio!
Do share, then the thread might go somewhere.
