Welcome to the forum from Western NY. I don't think you'll have a drone problem if you change the mid-muffler. My understanding is that the resonators at the rear of the car are primarily responsible for eliminating drone. If you replace or remove the resonators, you may experience drone.
Nice whip! Normally, you'd be safe getting rid of the mid-muffler, but in your case, you've already removed the stock resonators, so unless you find someone with the same setup as you propose, it's hard to say whether you'll have an issue with drone.
Personally, I would have swapped in a complete take-off dual exhaust from an R/T before I spent that kind of money on the 2-into-1-into-2 stock exhaust. That's what the GT V6 comes with from the factory.