If you have the spacing right you should have a lot of float -- like your feet turn without any scraping sensation at all. I've never installed the CB cleats and not needed to use the plastic spacer. Without the spacer my feet are tight against the pedal and clipping in and out is difficult.
If the cleats are used, there's a good chance that they're pretty worn. Those cleats are made of butter. I generally install new cleats every year on my CX shoes. Unfortunately brand new cleats don't work as well as very slightly worn cleats, so I try to get them on in time for a few weeks of practice riding before I start racing with them.