I considered a similar design. I am limiting myself to the material I have on hand, which are 2" bar drops - I have half a bucket of them. I could not figure out a way to make them work well.
If I have to buy material, it's cheaper to just buy a ready-made, chrome plated cymbal boom stand or a complete clamp-on boom extension arm. I did find a source for a 24" stainless tube for $13. I only need a little piece for it to accommodate the clamp I'm making.
It's for the back two cymbals.