I am currently a StyleArc 18, but if I lose a bit of weight (as planned) I'd be a 16. The envelope patterns break at that point so don't know what size to buy....
It would be much better if SA did overlap their sizes. I struggle a bit with their sizes anyway. I think they're more like RTW? I've ordered the Elani tunic top and intend to make up the size 16 with an FBA of some sort, but will no doubt agonise over sizing first!
They are more like RTW sizes, definitely not like the Big 4 patterns.