I've been :lurk: ing here since this thread began, but it's been a busy holiday season... First off, great work among the fabricators here. It would be amazing if we collectively came up with the means to assemble a reasonably priced kit. I for one like dual outlets, regardless of whether that means two mufflers or one. It just fills the space nicely. License plate placement is another issue, especially if you don't like the idea of it hanging way down below your beautiful muffler mods. That's the reason I went with mine above the muffler, even though it unfortunately obstructs the rear view of the muffler a bit.
The reason I eventually abandoned my underseat setup for the tok tokkie underbody design was that I ride two-up all the time and we were hitting the pipes and muffler with the rear tire on big bumps, sometimes hard enough to send an impact up through the seat. Another problem I had was melting bits on the undertray. I tried to cheap out and modify the stock plastic undertray, which later melted in several spots (despite heat-resistant sheeting between the undertray and exhaust). Last but not least, the muffler guy I used did a hurry-up job on the mid-pipe-to-muffler section with mild steel, and after seeing veefer800canuck's stainless and Wolf mid-pipes, I'm pretty underwhelmed with mine.
So I built one like tok tokkie's last spring. After living with the underbody system for a season, I found it had several significant drawbacks (not that I think tok tokkie is anything but brilliant for designing it!!), so now I'm back at the drawing board... again... <_<
At this point, I'd recommend the following for any complete underseat system: An undertray made of thin ceramic-coated aluminum (I think Rob would agree that even thinner sheet than he used would be fine) with as much room as possible underneath for the bend connecting the mid-pipe and Y-pipes (it needs to be as *up-and-forward* as possible to avoid tire contact later. Ovalled pipes (much as on the 6th gens) would be the best solution yet. Carbon-skinned cans would be best for limiting heat transfer. The grommeted stays for the tail plastic (at the back by the lights) need to be replicated to avoid cracking plastics (as happens with Wolf systems unless modified). Re-positioning of the CPU is required. Shimming the shock (especially if you ride two-up) will likely be necessary, no matter how compact/ideally routed your system is, to avoid tire-to-muffler/pipe contact over big bumps. License-plate location is still an issue, maybe one best left up to the individual (I recommend Lite 'N Bolts for license-plate lighting).
First one to assemble a plug-and-play kit that addresses all of the above for under $1000 wins!!!! :D