A lot of the flies used now are 2/0's, even 1/0's . I would guess that 2/0 Gami SL12's are probably the most common hook around Islamorada. Most of that fishing is done in very clear water, hi-vis and high sun. I rarely get a chance to fish like that anymore. Most the guys I used to fish tarpon with who lived here are now in the happy fishing grounds, and the last of them has Alzheimer's real bad.
Hardly anyone uses 5/0's but me.
I like Gami octopus 5/0 offsets because they are made from thin wire but are strong yet don't snap off. But that's because I am usually fishing backcountry in cloudy water where the fish eat really big flies readily, and fishing with guys who want to catch a tarpon instead of practicing their casting at hundreds of them with lockjaw.
They are much easier to catch when they are actually feeding, and that's what my northern buddies all want to do - catch them. We usually get there late in the afternoon at about the time most all the guides are leaving and fish into the night, if necessary. Few guides do that.
Most of my northern friends, who are ocassional fly fishermen, do not cast well enough to have but a miniscule chance of catching daytime ocean fish.