BTW, that diverite pouch is big. You should be able to fit everything you listed with room to spare. I usually keep a mask, snorkel, dsmb, reel, light, and nautilus lifeline in mine. I started with a "regular" dry snorkel. The snorkel did stick out the end of the pouch some. I later switched to a roll-up snorkel.
I guess I've gotten complacent. It just occurred to me that I did a whole trip to Cozumel without any backup stuff in pockets. I did clip the light, lifeline, and dsmb elsewhere but I didn't carry the spare mask or snorkel.
When I carry a camera (gopro or otherwise) I usually do not want it in my pocket. In part because I might forget to use it, but also because I want it in the camera bucket on the boat so it's less likely to fog. I have a boltsnap on my gopro (or other camera) handle and I clip it to a chest d-ring if I'm not actively using it.