Hah, I went from 8g to 00g in 11 months, and that’s not the fastest I’ve seen (I’m not especially proud of it, it just happened.) I’ve run into this issue. The extra flappy skin is recoverable and can be made to recede, but it needs to be dealt with in the moment as it’s some combination of overstretched skin and scar tissue and if you don’t deal with it quickly it’ll become permanent.

My recipe for dealing with it is the following. Get through your stretch. After the stretch has stabilized and loosened a bit (typically this happens to me in like 4-5 days), take the piercing out and leave it out for short periods of time - like 10-15 mins and moisten it with scar gel (which is basically a hydrating agent). The skin will start to bounce back and recede. Reinsert the piercing and do this regularly, like once or twice a day for a few days. You’ll basically coax the flap of skin back inside. However, you need to do this in the early days after the stretch, while the “lip” of skin is still malleable.