Which Lowepro Fastpack for Nikon D7000 w/ 18-200mm attached?

I might also want to carry a secondary compact lens and a flasher. I'd like to choose the smallest bag that fits my gear, so I'm sure I don't need a Lowepro Fastpack 350.
Is Fastpack 200 enough, or do I need a 250?

Added (1). I have already checked Lowepro's bag finder, but it won't let me configure whether I want the lens to be attached on the camera, or just separately stored.
I'd like to have the 18-200mm lens attached to the camera, so that I can just take it out and start shooting pictures right away.

Go to the Lowepro website

http://www.lowepro.com/intl

and click on bag finder. Answer the questions about the type of bag you want and the size/quamtity of equipment and it will list the best fit.

I use Lowepro Fastpack 250 AW and my D5000 with 18-200mm lens fits very well in the compartment.

I believe Fastpack 200 should also be able to accommodate; if it doesn't, then you may open up the Hook-and-loop fastener compartment below the lens and make place for the long lens.

Alternately, you may choose to keep a shorter lens (like 35mm or 50mm) with the cam and keep the longer lens in the lens compartment.

I'm very satisfied with my Lowepro Fastpack and have been using since last 1.5 years. Indeed a good choice!

Buy a Think Tank "Change-Up". I keep my Nikon D90 with 18-200mm lens, a second Tokina 11-16mm lens (a good sized lens), and a SB-600 flash in it. Very small, very compact, and lightweight.

Think Tank bags are professional quality, and made much better than Lowepro (although Lowepro are nice enough bags).

One of the founders for Think Tank was Lowepro's designer before he moved on.

http://www.althephoto.com/gear/excursion.php