I have Medicare (A & B only) and GHPP. You are correct to opt out of the part D portion. I get all my rx's from mail-order pharm, and all of my drugs have been covered, and I've never had to pay out of pocket for anything. The only exception is when I walk an rx in to the local pharm. They don't know how to deal with GHPP and it's a pain to explain, so I just don't do it. Instead, I make sure that all docs call my rx's into the mail order pharm. (I only have this problem when I've seen a dentist or non-cf doc and the rx's they might hand me.)
GHPP will pick up the balance that your other insurance(s) don't cover, except if you have a co-pay. All other insurances are billed first and what remains is paid by GHPP, though this may take months, it will be paid. GHPP does NOT pick up "co-pays" by other insurance carries (if you have Ins through a spouse or work).
Bottom line, GHPP will cover the 20% that remains after Medicare.
GHPP will pick up the balance that your other insurance(s) don't cover, except if you have a co-pay. All other insurances are billed first and what remains is paid by GHPP, though this may take months, it will be paid. GHPP does NOT pick up "co-pays" by other insurance carries (if you have Ins through a spouse or work).
Bottom line, GHPP will cover the 20% that remains after Medicare.