We store things like diving flags, fins. snorkels, shoes, etc all over inside the hull, yea once in a while you might have something hang up on a line, I had a diving flag get tangled up in the rudder up/down line once, but it was easy to get clear and didn't cause an issue. Since then I try to keep everything tethered, or it can slide into areas you cannot reach.
What we typically do is like Tom suggests leashing everything in so it doesn't fly around in there. We have a couple strings with clips tied to the holes on the inside of each of the round twist and stow hatches, I keep a dry box tethered under each hatch (for wallets, phones, watches, etc). I attach my mask and snorkel to one of the several of the plastic clips attached to the tethers. Dry bags we just stuff into the hatches. I have one stuffed dry bag with tools, a first aid kit, a rain suit, and the night time navigation lights that I always throw in the bow hatch before launch. I don't think it matters a lot where you put the stuff until it gets over a hundred lbs. We typically put big things in the front hatch like tents, etc. I don't think the inside of the hull is completely dry on any of the TI's, on a typical sailing day I can get a cup or so of water inside the hull, on a tougher day maybe a quart. The water just finds it's way in, so we just keep anything that has to stay dry in dry bags. Cell phones we store in the dry boxes below each hatch.
When we go out Island hopping we typically take a big cooler full of beer, food and snacks, we try to stow that as far aft as possible either across the stern or near the back of one of the tramps.
Scuba tanks we typically lash to the rear AKA with flat kayak straps. The BC's and dive bags we lash to the tramps typically.
You will find the TI has ample storage especially with the trampolines.
Hope this helps