Wow, I've never even known that they had different thicknesses.
I have built hundreds of t/cases, and we just have a bin with a thousand inspected good used clips, and we just throw a set on and get on with our lives.
I would say to mic your clips, and get that same size. To be honest, I have never had a clip that was to thick and would not fit, so I suppose you could just go with a thickness that is in the middle of the range that they provide.