I had a combined 18 colics between 5 horses when I fed my minis baled hay so they are now on a diet of half pellets and half chaffe (chops.) We use the Triple Crown brand bagged forage, the Safe Starch when our stores carry it. I like the consistancy of these MUCH better than always wondering if they are going to react to different bales negatively. And TC adds the probiotics to all their feeds, which was a plus for my sensitive little colicker. Also, they take up just two tubs in the tackroom, as opposed to the big horses' hay barn which is piled to the roof with bales that I get to bring in as I need them.
If you soak the pellets or cubes, it does take them quite a while to get through them. And they tend to graze on chops like they would hay. The brand I use doesn't soak that easily, so I feed them dry, and their pound of pellets with about a pound of chops usually takes everyone around 1.5 - 2 hours to finish. My little guys eat slow!!! They gobble up the pellets, play with the chops, toss them around, pick at them, and then eat them up lol! I don't actually weigh anything, but I'm guessing those are pretty accurate numbers because they all get the same amount and I do measure how much we go through a week.
As for stalling, my minis are in their stalls all night because we have too many critters out here for me to feel comfortable leaving them out. I've never had or really even seen a mini have issues with being confined. I think because big horses crammed into a 10 x 10 stall can't move around as much and are more likely to have a problem with it... whereas a mini in the same space can walk around and enjoy himself. In the biggie boarding stable we were at in So Cal, out of 75 horses in the barn: 7 were cribbers, 4 were wood chewers (including one door-eater who eventually had to have his top door closed all the time), 2 bad stall kickers, 1 weaver, and 3 stall walkers. The majority were just fine. The ones who got regular excercise and had jobs usually handled it better.