I realize this hasn't been posted in a while, but I felt I should say a few things.

The Colt series of toys, as far as I've seen, are intended, or at least marketed, towards the gay or bisexual male. At least, that's the impression I've gotten after reviewing the Colt Butt Man Masturbator, and more recently the Throbber.

While I agree, no flared base can be a problem, I didn't have much trouble using this for anal.

I'm not sure whether a beginner could handle it. I didn't have much trouble, and honestly I don't go with anal but maybe once a month or so.

As for being worried about it stopping, you can get some rings on Eden. Not cock rings, but ones for vibrators. Just snug it down two or three inches from the base, to use as a guide for when to stop sliding it in. As long as it's a good snug fit, it shouldn't slide or move along the base.

I suppose if you are really worried, you could try getting a snug ring, and some super glue, to permanently fix it in place. Though it would be wise to do some extensive searching online on the subject to make sure you don't ruin your toy.