Well, I'm firmly of the camp that says make shit up if you have to, disregard pieces of canon if you have to, as long as you're hanging true to the essential core of the characters and universe. (I catch flak sometimes for this, but hell, you can't make everyone happy, and a camel is a horse built by committee, and the sun don't shine on the same dog's ass all the time [to continue the parade of aphorisms].)

It's that whole thing of separating the essentials from the non-essentials. I really don't give a toot when exactly Mulder went to Oxford, for example, but it really does matter to me that he has a *brain,* and so does Scully, and when they do damnfool things they need to be the kind of damnfool things really brainy people might do, as opposed to adolescent nitwits or greenhorn rookies. And you've got an excellent sense of such distinctions, so fanwank away, is what I'd say.