So the guys at Nerf Mods & Reviews presented enough convincing evidence to warrant me picking up and, subsequently checking out the Vigilon. Obviously the Torsion Spring Mod on this is a must, but I remember LordDraconial trying to fit a 6th Disk in there. I figured it was worth investigating on my own. The solution I found doesn't involve cramming an extra disk in there, but rather making use of the Vigilon's priming system. Check out the video below to see what I mean.
This same idea works with the clip system for Vortex on the Praxis. It won't work on the Nitron because of the priming system on it. Here's another video that shows the Praxis' loaded with an extra dart. Put that Gear Up! disk to use!