I don't know how to do links, but you can find me on Utube under smittyslingshots. I think 3/8" steel is way too big because 1/4" is plenty for strength. The 3/8" will only block more of your view of the target. You could use 5/16 to bend cold though. It will be hard to bend, but a length of brass pipe should do the trick without tool marks. The only reason I like to use some heat is to make it easier to bend and to relieve internal stresses built up by bending. A cheap propane torch will help a lot, nothing fancy, but it isn't absolutely necessary. You can clamp two 5/16 " bolts in a vise and mark your rod where you want to make the bends if you don't want to make a jig. You can also make the ears like the ones in the picture to simplify the process a great deal. Using a polishing wheel with some jewelers rouge/polishing compound is important for long lasting rubber performance. .050 is a good gap for swapping out rubber.