As a frequent flyer, I think you're more likely to make it than not, except for a possible delay. But then, if there's a delay, you might not make it even with two hours in between.

Charlotte is small enough and fast enough to make it. You can always be moved (either by telling someone in customs or asking the other folks in line) to the front of the line (I have to do this on a regular basis in Calgary with no problem).

If you're doing carry-on only and are willing to tell people in line at customs that your plane is boarding and could you please move to the front, you'll make your flight.

Also, the airline computer systems actually won't book you for a flight that you can't make. I've tried on every airline (I fly 45 weeks a year for my job) and it just doesn't work. It's programmed into the system to not allow it.

I still think 50 mins is asking for trouble. I just flew in from IAD to CLT, and the plane was delayed 25 mins due to storms. Several ppl on the flight missed their connections, because they had booked too close. If you like to live dangerously, go for it...I don't like to spend extra time in airports, so I like to allow plenty of time to get to the gate, rather than have to lay over any more time.
In any event, good luck. And, welcome to Charlotte!!