The guy I chatted with was called 'GaryTech' which was very helpful. You can catch him normally during Live Chat hours the times I've used that feature. The delay time to replies is reasonable as I'm sure most poeple ask quick questions and I think he said he has a 10:1 ratio users:techsupport. Wait times on average are ~1-2mins per reply which is reasonable given the 10:1 ratio.

From my experience with jerseys having bought jerseys for the first time last year and over time learned a bit from them what you want is to measure your chest (if you have a flexialbe tape measure) under normal breathing and take that measurement. Then take a measurement at max. inhale deep breath. Keep those measurements handy in the wallet beside the shoe/shirt/pant size and write down your EURO and USA measurements and keep in the wallet which helps when you're looking for stuff.

I find if the garment has a lot of stretch to it then the normal breathing measurement would work well as you have room to expand as you're maxing out your lungs if you train that hard. Anything with spandex/lyrca will expand. Polyester will stretch as well but not as much as the spandex/lycra would.

A good compromise is to take a middle number between your normal breathing measurement and your max inhale measurement and you will have a formfit-relaxed fit so you have some play with. Most of the times most poeple don't max out thier lungs.

Hope that helps.