Unfortunately, I don't how helpful I can be on the sizing front - unlike your "gumby" physique, I'm built more like homer simpson My inner belt (also ATS) and war belt are both XL. My guess is you'll be ok with the Medium simply because the belts are designed to have the buckle exposed, so when they say it fits a 30" waist, it's assumed the molle portion won't be touching. So, for example, the XL is listed as 38-42, and I was around a 38" waist when I first bought it. If I took the war belt and tried to wrap it around my waist without the inner belt there's no way the two ends will touch. Not sure if that makes sense.
You can see the space to the sides of the buckle on my belt.
If you're very concerned with sizing, you may want to consider the BFG belt:
http://www.blueforcegear.com/products/SOC%252dC%E2%84%A2-Modular-Padded-Belt-Kit.html
It's a LOT more expensive, but has built in adjustability.
As for liking it - yes, I do. I'm quite happy with the setup. It's been thru 2 MDTS carbine classes and an MDTS shotgun class and no complaints. I liked it so much I brainwashed another member on here into buying one, and he seems to like it quite a bit as well. Now, if I could just lose some weight so my gut isn't hanging over the damned thing, it would be even better