You’re not going to get much more precision and rigidity than where you’re at right now. unless you want to go to hardened stainless rods. At 25mm and 30in lengths, well i don’t know what that would cost. if you go any smaller on the emt size you will lose rigidity. if you go any larger than 1″ maybe 1 1/4″ You’ll start to lose rigitity as well. and cost effectiveness. keep focusing on making your awesome designs better.