Explant of silicone subglandular smooth mentor implants, how much capsule to remove?

Dear afawnf,
it is hard to tell for sure without an examination. Generally speaking, if your capsules are thin then only implants can be removed. If you are considering surgery, I would suggest you consult a board-certified plastic surgeon. Only after a thorough examination, you will get more information and recommendations.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

As you suggested, this can be an individualized answer. With a soft, pliable capsule, there is no reason to remove any of it. If the capsule is thick and calcified, I would usually remove all of it, if possible. No reason to retain a mass of thickened, calcified tissue that might be palpable.
Other than that, there is no reason to be concerned about leaving the capsule. It would be a good idea to suture the front and back together to hold the overlying in breast in place and decrease the chance of getting a fluid collection or seroma.