Are you looking for advice on which ruck to look at or...?
All in all, with the CPC alone, it'll be possible. Depending on the ruck you use, the waist belt will sit on your hips on just above, so clear of the bottom of the carrier. The problem arises when you use the low-profile belt (or any belt) because you'll likely be overlapping that belt and your rucks waist belt.
This is all solved obviously by either not using the ruck waist belt or sticking your low-pro belt under the ruck lid while you're tabbing.
Now, that all said, it's also gonna be important to find a ruck where they foresaw the end-user wearing body armour. Mystery Ranch has done this (BVS system), I'm sure there's more. I say this because when I wear my issued frag vest and then my issued rucksack, it rocks back and forth because it doesn't conform to the shape of the plate.