Thanks for the answers.
I was probably reading the F1D forum and applying something there to all indoor models. At their scale you have to think differently.
Well, the same thing applies even to SO Wright Stuff (which are significantly heavier than F1D) or LPP.
LPP might be 2.8 gram loop 23" long. Very clear and consistent measurement that is easily comparable.
Saying 19" loop of 0.055" doesn't give you the right information (total weight) that is needed to make up an identical loop.
Again, this is for indoor competition flying. For sport flying or general help, saying 19" loop of 0.055" will convey something pretty meaningful and get someone in the right ballpark.
But saying 1.5 gram 19" loop of March 2016 Tan SS would be much more precise.
As an exercise, try cutting precise lengths of rubber, then weighing them on a milligram scale. You'd be surprised on the amount of difference in weight. I've see upwards of 10% on occasion.
This is when I finally understood why density per length is the right way to go.