I'm kind of laughing here reading about you guys chatting about whether or not it is safe to let your buns outside to play. So, have none of you ever let your buns outside? It's honestly not that big of a deal to do if you are out there supervising. Obviously they would need a more secure area if it was unsupervised. We have an unfenced grass area that I will take my buns out to for playtime after the snow is gone. No leash, no fence, and they do just fine. They always stay pretty close to me and just hop around and explore. Even if something spooks them they don't bolt away. Usually they just crouch really low in the grass or run to hide by me, til they're sure everything is ok. Sometimes they'll decide to explore at the far end of the grassy area, and I'll follow them where they go, but usually I just sit out there on a blanket and watch them. Most of the time they head for the pine tree and like to play under there, which I hate cause it's a pain to get them to come out when it's time to go in. Lisa, just take a blanket and sit out on the grass(if you have grass, we still have a ton of snow) and watch them play, you'll love it! If you are worried about them slipping through the chain link, then when one of them gets near the fence, just stand there by them to see if it's even possible, and stop them if it is. I would think Archie would be the one that could slip through, if it is possible at all. IF they can slip through, you could always run chicken wire along the bottom of the fence to stop that from happening. One thing you have to kind of watch though, is if you have much grass growing yet, then they won't be used to it. So if one of them starts to eat a bunch, then you might need to limit their time out there.
I think it's their whisker width that lets them know if they'll be able to fit in a space, but that doesn't always necessarily stop them from trying to fit somewhere where they really won't fit.