Since you're afraid that the 210mm lens is too short for your purposes, the next steps up are 240mm and 300mm. I don't suppose there's any chance that you could rent or borrow a 300 for a week? That should give you a chance to see if a longer lens is really what you want, before committing your money to a purchase. Certainly with your camera the necessary bellows extension for the 300 is no problem. You might even find yourself wishing for a 360--there's no accounting for personal taste, and you might prefer the increased compression. So trying out a 300 sounds like a logical course of action to me. I certainly wouldn't recommend buying a bunch of lenses which are close to your 210, which you already have--I don't know why some people in this thread have recommended it.