I do up to 15 segments a year with my dog.

You SHOULD be ok if it's a soft carrier, as the soft carriers just squeeze in a bit. However, it is up to the agent at check-in and since you're at MCO, that's a contract agent not a direct employee so your milage may vary.

Also, every aircraft is different - AC lists the specs for the different aircraft and sizes on their website of what is allowed. Also even on some specific ones (737 max for example) you have to be in row 2-4 in J but also seats A or F, C and D are not allowed. etc. So you need to call in and make sure not just your row but also your specific seat is allowed to have a PETCO.

The biggest thing that check-in agents have checked with my dog on a frequent basis is a) do they look healthy and safe to travel (mine is) and b) do they have room enough to stand-up and freely turn around inside the carrier when it's closed (mine does).

Also make sure to bring some kind of bottle for them for water that you can fill up post security. I specifically use the below one while flying because any water the dog does not drink can be put back into the container by pressing the button which avoids all kinds of problems on planes.