I'm totally comfortable with people calling me whichever name they wish. I'm Charles to most everyone, but a few friends have actually come up with "Chas" as a nickname all on their own, and I'm totally happy with it. There's a whole segment of people from my past who know me as Charlie, which is jarring to those who hear it now, but that, too, is totally comfortable for me. I'll respond happily to any and all of the above.
I actually always rather liked this (antiquated) abbreviation for the name. It's what I've generally used online in some variation or other, which probably started when I wanted something short, so I automatically went with it when joining HHW.
I think the only related name I can happily do without is Chuck. It's fine on other people, but I am not a Chuck.