One foot up is okay, but can still pose a danger to the kits. I prefer not to have any shelves in my cages so mom has to be by her offspring. Sometimes moms, especially new moms, go up high because they are uncertain of what to do. This leads to the kits not getting proper nutrition. Also, should mom give birth on the shelf, it is possible for the kit to be hurt if they fall after birth. It's not a huge distance, but it's enough if a newborn kit lands wrong. I would take out shelves until after kits are born and are able to be without mom for a while.
Something to consider with colony breeding - not all chins are great at it. Sometimes, what seems like an awesome group isn't so awesome after kits are born. Some mothers become super protective, dads can get super spazzy, other moms may be mean to offspring not their own. I have used colony breeding for many years, but I'm also very careful to keep an eye on them and am quick to act if needed. Also, I know it's a strange thing to think of, but color of your chins together. I've heard from several different people that they had females give birth at the same time, and they have no idea whose kits belong to who because moms and dad were all beige. Just something to keep in mind.
Lastly, you'll want to be very vigilant of your moms and remove dad once pregnancy is confirmed in any of them. Otherwise, you're going to risk breedback after breedback. It's not healthy for the female.