Well, a little epoxy never hurt anyone.
I feel like there is a better way to do this... is there enough room inside the shell to fashion a PVC brace for the parts in question?
EDIT: For format.
Yeah, you guys are totally missing the point. Sure, you could go making PVC or poly-carbonate brackets and support systems, heck, you could rebuild the entirety of the internals while you're at it! Replace the plunger head, build a poly-carbonate catch to replace the original. But that's not the idea here.
This is the way it is because it works, it's easy to do, and makes this mod accessible to those with little to no experience modifying blasters. Granted, using epoxy is not the most strenuous job in the world, but more people just have hot glue and duct tape off hand than do epoxy and materials to construct some sort of bracket. Note the beginning of the entire writeup: "But they [other more in-depth BBB writeups] are all too complicated for someone who is new to modding. And more importantly, I think it is a waste of time to put so much work into what is, at it's core, a fundamentally mediocre blaster."
Also, Beaver, cool stuff, though I recommend adding some electrical tape in order to seal (or get as close as possible to doing so) the joint between the plunger tube and the coupler assembly. You've noted that you've maxed performance, so this may or may not help you, but I've found it to really make it seal nice, and if you wrap enough around, it can also help with that rotation issue. Important to note though, e-tape is less common to just have around the house, so again, in the interest of this being accessible to more people, duct tape may be the only option, and that's totally cool too.