They make a special tool for crimping these clamps. I picked one up, I think just at Sears, maybe at Autozone or something. With that tool, I found that I could 'afford' to spread the actual 'clamp' section out slightly with some needle-nose pliers, allowing me just enough size to get everything assembled, and then still get a good crimp with the special tool.

Yes, on a PS rack I've used nice big zip ties to good effect. A CV would make me a little more nervous, but I suppose as long as it's a good-quality tie...