I have an 8.3 mm rope, just under the 8.5 listed. Do I chance it and get this or just stay away?

yes it will work. I use it on 8mm rope. be sure to go with a larger HMS girth binner. Petzl Attache is a good biner to use on thin ropes.

Since we are talking about a piece of (relative) safety equipment, the question you pose a difficult to answer. There is the absolute "will it work?" (ie: assume Wild Country was conservative in its rope tolerances and the 8.3 is a go), and there is the "it kind of works" (ie: it will take a bite of rope but there is little to no camming action taking place). The bottom line is this, 0.2 mm is very small, and this great hidden gen of hardware could likely be a great addition to your kit. So, I wouldn't be afraid to buy one here on BackCountry, and check it out at home or at the gym where you can safely test it out. Heads up though, DO NOT load it with any substantial weight before checking out the next paragraph The FIRST thing you want to make DAMN sure of is that there is that the cam is sufficiently displaced so that when you place a load on the rope man that the cam is in place because of the pinching force on the rope and not because the cam lobe has hit the stops. This is critical because you don't want to be climbing your rope with just the little teeth. That would be, one, horribly unsafe and, two, probably destroy the rope. When used properly, in my experience with it, this device does not shred the rope at all, and is safe. I hope that answers your question enough. I can only testify for as low as 9.8mm with this device, but if you look for the things I mentioned, and everything checks out, you could be the proud owner of a Ropeman MkII. If you find that this device does work for you, I almost guarantee you will buy two. Climb On.

It will *probably* work. Each rope is built a little differently and depending on the core:sheath ratio, the amount that it compresses will vary. Chances are you're fine, but I would test it, and if it doesn't work, there is always backcountry.com's awesome 100% return policy!