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Well, depends what a real good job is. Structurally sound and stong = essential. Cosmetically perfect = couldn't care less. It'll all be covered in tape anyway.
So, following simple logic, if I get some 22.2mm steel tubes, then use a website like this to calculate the mitering and carefully spend a couple of nights filing it to shape, then all I need is someone with a torch to braze them in place, right?
It's such a simple shape that I'm assuming it can be done without a jig, or not? Just mark on the angled side tubes where they connect with the straight one, and set the thing on fire (I say 'just', but who knows).
Tempting.
I should probably add that you need it 1000% if you want a real good job. You could get away with less if you wanted to compromise