Howdy!
Welcome to SB!! :happywave Put us in your computer's favorites and check in often. This is a great place to learn, compare, argue Look around our various forums - everything from New-To-Scuba to Instructors-Only to Dive Medicine.
Pony bottles are very popular for discussion around here - Por & Con. I don't dive without mine, but I'm just now getting it where I can hang it upside down and turn it on and off easily. Some would say it should be carried in a way that it can be handed off, but I am not interested in handing mine off. It's first and foremost for my needs, although I will offer air to anyone who needs it - from my primary or pony. They just have to follow me.
When I compared sizes, weights, and prices, I chose a 19 cf. The 13 cf is not that much lighter or cheaper, whereas the 30 cf is a big jump. A 6 cf might be enough for ascent and stops, but as long as I'm going to carry one, with a reg and hangar, why not spend/carry just a bit more.
I'm not bing on cameras, but I'm hacking around. If it weren't for digital, I wouldn't bother. BTW, when you get to Cozumel, be sure to tell the Dive Guides (some of whom may actually be Dive Masters?) that you are a Master Diver, but you've never dived off a boat or in the ocean.
don
BTW - Did you set up your Profile? Some ideas for your Profle might be taken from looking at mine. Click on my Username to the upper left, then click on my Profile, and see what I've done. For your's, click the [CP] in the upper left of the screen, then click [Edit Profile]. If you need any more help, PM me direct.