Thing is with those smaller Cannondale is that the clearance weren't decent to begin with as you've experiences, fitting mudguard will quite likely to be a real struggle.
I've got 25c OPs on Pacentis at the moment with a set of clip on guards, and there's plenty of room. I recon I could make it work, given some eyelets...
The eyelets is the least of your concern (PDW designed to be fitted without eyelets).
Your problem is the gap between the brake and the top of the tyres, if it look ok, then chance are it may not fit, especially when the brake likely to fold against the mudguard when operated.
Thing is with those smaller Cannondale is that the clearance weren't decent to begin with as you've experiences, fitting mudguard will quite likely to be a real struggle.