The downside of all "trapped ball" chastity devices (ones that use a ring to hang on instead of a belt) is that they can get pretty uncomfortable with pinching and chafing. Especially for people with nuts that are high and tight, like me. [That is my problem. I keep saying I have small balls... which is still sorta true... but the bigger issue is that they're very high and tight. So I can relate. --TFG]
If your CB6000 fell off because there was too much lube on the ring, then you could always get out by adding lube to the ring later. So that means the fit is wrong.
KeptForHer makes an insert for the CB6000 that is supposed to prevent pullout.
I haven't tried it myself, so I don't know how well it works. And I don't know if pullout is really the same as falling off. From experience, I would say that YMMV with every single device in the world. We are all shaped differently.
I have a belt I'm not using that might work for you, depending on your waist size.
It has both a belt and a ball-trapping loop, but tends to cause less discomfort (for me) than a CB6000.
If you're like me, it may still get uncomfortable as you cool off and your sack tightens up. That's the usual problem with trapped-ball devices. But it won't fall off. Also, it has an embedded lock, so there's no rattling sound.
I've used the Curve, the CB6000, the Chastity Steel, and two different Carraras (by far my favorite, but very expensive). I also have some Mr. S leather chastity shorts and a leather chastity belt that Skeeter at Mr. S made for me custom. I've tried on seedpods and boy trainers, and I've made various devices of my own out of fiberglass and leather. They all have upsides and downsides, and I don't think you will find a perfect one. And, if you read a review that says it works great, remember that that just means it works great for that guy.
For example, I love my Carrara belt, but like you I tend to sleep on my side, and I can only do that with a big pillow between my legs. Otherwise, the ball cover grill tends to dig right into tendons in my leg. (Here's a review I wrote for Metalbond: http://metalbond.thumblogger.com/home/log/2010/23/how-to-lock-your-cock-and.html )
Almost everyone asks me the longest time I've worn a chastity device, but I'm not going for any records. I'm more about using chastity in a scene as opposed to day to day. It's about that moment if you're whacking off when you just can't wait anymore. Imagine reaching that point but not being able to do anything about it. That's what it's all about for me.
Hope this helps
You know, I really agree with him on that last point. I think for me personally, I certainly won't be breaking any longevity records. One, I just enjoy jerking off too much, so even just a couple of days of deprival is pretty intense for me. (And stop rolling your eyes, it is for me, I swear.) But the main reason is *ahem* my BF enjoys having sex with me too much to keep it locked up for long. He does like the idea of me wearing it, but for him, it's eventually gotta come off. He wants to have fun, too, you know. :)
A few people have asked me if my boyfriend holds the key when I wear it. So far, no, I put it away myself. And in fact, often I've locked myself without even telling him. When I do lock myself up, it's because I want to, so there's not a lot of general fear of letting myself out too soon. It's also because I'm still sort of in the stages of getting a comfortable fitting size. So for safety reasons, I do want to make sure I have "emergency" access if needed. I suppose in the future, as I have more time, I probably will turn the key over to him. But to be frank, I'm a bit more into the idea than he is, so I can imagine often he won't really care about holding the key or not. Which is okay, as I'm perfectly fine denying myself a bit.
In any case, I certainly thank ccontrol for the advice, and I hope it helps others out there! If you want to know more, I also ran across a great article here. It's very detailed... almost to the point of overwhelming... but it really tells you nearly everything you'd need to know, and you may find it very helpful if you're new at this.