I have taken my pony to Bonaire in the past but on the last couple of trips I rented from Walt at RT.
When I flew out of Canada (Toronto) I packed it in checked luggage. I removed the valve and wrapped the opening with a couple of layers of plastic. I printed the rules and wrapped them around the tank. No problems.
When I flew out of the USA (Buffalo) I took it in my carryon prepared the same way. I made sure to tell security in advance and they were not concerned about it. They were more interested in my UW video housing.
With the new security measures, they are supposed to be restricting what luggage/items can be carried on for flights into the USA. In theory you should not be able to carry a pony in carryon, although on my last trip from Bonaire you would not even have guessed that the rules had changed as almost everyone had big roller bags.
Remember that you will need to get it filled when you are there. BDA did it for me on a couple of trips, although I had to "encourage" them. You'll also need to get a VI done when you get back.
I always dive with a pony in Bonaire, solo or otherwise. I find it easier to just rent the 27CF for the week from Walt and sling it. It has never been a problem. I have considered slinging a 63CF, but lugging the video housing is bad enough. If I did not have the camera that is what I would do. It costs nothing and all you have to bring is some rope a couple of snapes and a strap.
Where are you staying?