Hi Mindy's mom - I messaged you on your visitor site earlier - I'm not sure if you received a notification or not?
Anyways, you've probably already gotten around this issue, but I can tell you that I raised two cavaliers and trained them both on harnesses. Kosmo (my blen) was my first cavalier and on a collar in the beginning and he choked himself - the vet said to take him off, I did, and he's never been on one since. Faith has never worn a collar in her life - they both walk beautifully.
If you need suggestions on harnesses for a cavalier, let me know and I can give you a whole whack of suggestions