I have a friend who has a 2014 1LT Convertible, a couple weeks ago, I just helped him find a NPP from a 2012 2SS and installed it on his car. No need for modification for the exhaust to fit on a convertible/V6.
Regarding the flaps, they will stay open all the time. If you want to control the flaps, you need to buy the NPP IN A BOX. This is for those who didn't have the NPP setup from the factory. I never done it, but according to the website, it only takes 5 mins for installation.
http://www.nakidparts.com/id78.html With this, you will have access to control the flaps for, OPEN ALL THE TIME, OEM SETTING (3500RPM+ OPEN)
About how it sounds on the V6, for loudness, my MRTV1 is a little bit louder than the NPP, but the NPP is still pretty loud. What's best, is that the NPP is at the same time deeper!!
If I had the choice to go back, I would definitely choose the NPP for only spending $500 and maybe $180 for the NPP in the box.
For my MRTV1, I already spent 430 for the exhaust, 140 + 100 labor for the quad tips, 200 + 100 labor again for the SOLO J PIPES to get rid of the drones. =(