Last gas system I installed I looked at the UPC, Uniform Plumbing code. There were charts and examples that I got everything under control before I bought the pipe. Or so I thought. I pulled a permit, listing what I was connecting and when it was inspected. The inspector said that I did not need to run 1 inch to the first appliance. I had a friend who is a pipe fitter go through my calculations and he agreed with me. Location and size of load with the respective distances will help greatly when you do your lay out and calculations. I never thought about nor worried about the fittings in my system. Drawing the system out on paper was a lot of help for me in doing the calculations.