I sent a photo of my exhaust to TTI to see if they could tell me what I was doing wrong. It turns out that the transmission needed to be pushed up higher (I put it up another 1/2") so the pipes wouldn't hang so low. Next, the mufflers were just too close together. It turned out that the X-pipe outlets were 1" too close together! TTI mailed me a new X-pipe, and now it fits reasonably well. Not perfectly, as TTI said the muffler brackets should hang straight down, and on mine they're canted a bit. But good enough.
The pipes still hang a little low, but if I pushed the tranny any higher it would hit the brace under the tunnel sheetmetal. I already had to hack a big hole to get the tranny as high as it is (Keisler transmission).
I also had to reroute the fuel lines and protect them with an improvised tin heat shield.
The good thing about the X-pipe is I won't need a driveshaft loop!