Dave

I use ss hard lines everywhere---with a decent bender there isn't any problem bending up to .049 wall---generally I will use .035 for the bigger id.
A bigger roadblock is making AN 37 degree flares in the ss----it takes a GOOD tool for 37 and a 45 can't be used----if you don't have the 37 tool use compression fittings on it----
For templets, I use a lot of coat hangers or welding rods---

Jerry