This is exactly what the Infiniti Motorsports Helmholtz exhaust design does. Many exhaust designs have taken the Helmholtz resonance idea and added a resonator on the J-pipe to provide the best solution to reducing drone. The key, as you mentioned, is the length of the neck: Helmholtz resonance - Wikipedia. I would highly recommend adding a resonator on the J-pipe to improve results and reduce the required length of the neck.So I was reading a bit about J Pipes. The concept seems pretty slick. It's basically a pipe that is T-ed into the existing exhaust and capped at the end which acts as a resonator for drone.
With my current setup, I have two resonators on the mid-pipe (aFe Power Y-pipe and mid-pipe) and two Helmholtz resonators on the axle-back (Infiniti Motorsports center-exit kit). Overall, I quite love the sound of my setup, but I look forward to upgrading the turbos and hopefully improving the noise by replacing the restrictive OEM turbos.