I have a '08 7100.

In stock form it is certainly not meant to be ridden in dirt. There is a park here in Houston w/ crushed stone trails and the bike is a little twitchy when I attempt it. Stock tires were 700x35. I currently have 32's on it since I am almost always on pavement. I have no idea how large a tire it will accommodate.

I can't speak to the FX 7.2. I've never ridden one.

I would think that if you're going to be spending a significant amount of time riding trails and gravel/dirt paths, you'd be better off w/ a good used mountain bike. I don't know what it's like in your area, but here in Houston it's much easier to find a good deal on a used mountain bike than on a good used road bike. It seems as though there were a bunch of mountain bikes sold back in the 80's & '90's.