I started with Carnies three years ago. They are now one hive out of = lots. Lovely temperament** but the swarming is chronic, inbuilt and frankly a burden for the inexperienced.
Even experienced beekeepers find problems with them due to swarminess.
(I've just collected a large swarm which looks like Carnies from the markings. I will requeen later on with a different strain - probably Buckfast.)
They do,however , have several great advantages: hardy , well mannered and build up rapidly in spring. And they provide swarm collectors like me with free bees.
Don't is my advice.
** When pure. My second generation crosses followed and were aggressive on hive opening. I requeened