Hello Mick....
What is wrong with that one ???
If I may say, I think you may be a little bit overcritical there old buddy.
When you get the uprights in and soldered up to the top ring it will hold together nicely, then you can put the lower ring on and it will be very sturdy, There doesn't appear to be anything wrong with the pic you showed me there mate.
Had a look at mine earlier and the top ring is just under 4 Inch and the lower one about 3 inch.
hopefully a pic of mine during construction will appear as if by magic !