Does anyone know if there is standard hardware available for this sort of thing or do I need to make it myself?
Since it's (almost exactly) a 2:1 step down it can't be done with a single pair of concentric tubes. I'm thinking maybe one constructs the table with a 34cm tubular leg that fits over a foot and then one makes a 34cm extension which is inserted to make the 68cm version.
Or simply two legs, one 34cm and the other 68cm and you use one or the other. All this then needs is a thing like a giant wardrobe tube holder on the underside of the table and on the floor (It can be fixed permanently to the floor).
That's probably the bit I need to find/make, a short piece of tube with a flange that will fit snugly over an easily obtained size of tubing. My guess would be that it needs to be 10cm or so diameter.
Any ideas for suppliers and/or what such a thing is called?