Congrats on the Norinco. Personally, I'd say if your shooting small groups with it, don't worry about the slide to frame being tight, evidently you did a darn good job fitting the barrel and barrel bushing, in my opinion most of the accuracy comes from a nice barrel to slide lock up. I really don't mind a little loosness in slide to frame if it's within tolerance, the tighter you go the more you might lose a bit of reliability. Not saying a real tight one can't be reliable either, just sayin.... Anyways, unless you really like to tinker...which I sometimes have that itch myself, I'd leave it alone and enjoy the nice tight groups you already accomplished. Good job on fitting things together by the way. From what I hear those Norinco 1911's are made with some good steel too.
Jim