If the CX rims fit the same as Trad rims, the fit is marginal. The rim has to be big enough to go over the shallow retaining lips on the top edge, but also has to go over the plastic lug into which the single self tapper fits. If the screw is done up too tight, it may distort the rim enough to allow it to lift over the upper retaining lips.
In order to minimise distortion of the rim, (and to eliminate whistling), I apply self adhesive neoprene strip around the inside of the rim. This compresses when fitted and resists distortion of the rim as the screw is tightened.
That has worked for 16 years.
