Material: I print these in PETG which has a good balance of strength, print quality and thermal durability. ABS and nylon should also work except for nylon for the round clamps. It’s likely too soft to be an effective clamp, especially with a 1000mm boom.PLA should be avoided as it will get soft in the heat.
All parts print without supports except the 15mm Gopro clamp. That has “modeled in” supports between the gopro style 3-prong clamp and the part that clamps to the 15mm tube. That will need to be removed. I use a band saw to cut them out.