Troy Lee A3 helmet size

I've been eyeing up these lids for a couple of months or so and the thing that has usually held me back from a purchase is the sizing not being clear. I'm between sizes and I say between as the way Troy Lee have sized them for Europe is XS/S 51-56 M/L 57-59 etc, so there's no overlap like there is with most brands, or even a meeting up of sizes.

I thought i'd send Troy Lee a message to clarify the sizing, but there looks to be a 3-5 day reply in place currently, which isn't helpful when i'm itching to buy now.

Normally, with lids, i'd prefer to try before I buy, but I can't find these locally.

So, do I size down to small seeing as i'm about 56.5cm and in no man's land. Is 51-56 Troy Lee's way of saying 51-56.99? I'm sure they must have lost a few sales with people in the same boat, unsure of the sizing and being just outside the size of a particular helmet.