just finished making an underbody exhaust using a Dsection xr50 can, some GY6 header and the stock header. took about an hour to make with a total cost of $34. the tip of the can is angled so it blows the exhaust away from the tire. sounds great and no back fire.
I really wanna do this too, but I'm worried about it bottoming out. I don't intend on doing anything crazy with my Grom, but I've had cars with low hanging exhausts (doesn't help they were lowered) and it seemed like I couldn't go anywhere without scraping something.
I'd like to hear how you're doing with it after a few months of daily (or almost daily) driving.