[JMay]

Kevan,
             Like you I print the guide holder separately, to guarantee a  smooth surface for the guide to rotate onto, and there is the other bonus that you can after printing add a spacer to the guide well to raise it further for certain guides. 

Looking at the Spirit CAD image have you printed this yet and how did the rear diffuser come out as can see overhang and shallow angle issues there that may need support added.

Cheers
             John.