Perhaps this is more of an anti-tip, but here it is anyway.
As we all know, sometimes 250R parts fit, sometimes they don't. In this case, it didn't. I tried a Sunline Case Saver (Part # 101-00-002) on my 2004 CRF250X, and the chain rubbed on it big time. $30 down the drain. I think it's because of the D-ring chain (or whatever it is) that differs from the 250R, so if you aren't running the stock chain and you have the offset spacer, you might be able to get it to fit.
Incidentally...anybody interested in buying a slightly scratched but never actually ridden Sunline Case Saver for a 250R?