something that you may or may not have considered: launch lug placement.
with my Tank Killer, the toilet float nose cone would normally have required a considerable lug stand-off. Instead, I routed launch rod with an extra “lug” that ran parallel to the main rocket body THROUGH the cone. You may find this workable with your large ball forward section. It will help if you run a soda straw (or a MicroMaxx size body tube or equivalent) alongside an extension of your body tube INSIDE the ball. I suspect you are planning on the ball splitting in half and holding the chute. If you run a stuffer tube forward, put a plunger or piston in the forward half of the ball for alignment, and use a soda straw parallel to the stuffer tube, it will be easy to thread the rod through the tail and and forward end lugs (and the internal lug causes no DRAG!), and a small hole in the forward half of the ball will need to be lined up at each launch, but shouldn’t be difficult.
in your case, with a short plunger or piston attached to the center of the forward ball half, you can probably go with no wadding or baffle at all. Just make sure you have good motor retention and the piston slides easily. You’ve got the whole world’s (or moon’s) worth of space for shock cord and chute, so packing should be loose AROUND the stuffer tube.
I am no expert in stability, but if you aren’t a purist, running the ring OUTSIDE the outer boosters, moving it back a bit, and making it longer from front to back will help. Also, the tube segment caudal to the rear attachment fins IMO doesn’t add much in the looks department and really hurts you by pushing motor position caudal. Lose that segment and your motor position moves up that many inches, should give you a significant improvement in CG.
another option is adding a SECOND ring around the tail section. It is still in the “shadow” or slipstream of that big ball, but hopefully some of the airflow will flow back medially past the ball and make your rear fins effective. I like rings for many reasons, two of which are
1. They provide a lot of surface area
2. That surface area is displaced outward from the body, so it has even greater effect,
Then again, nobody has ever accused me of being a purist, so the cosmetic effect of the above changes my not be acceptable to you.