Status update: This thing has been running pretty much trouble-free for a few days. Initially I broke the intake that I made, so I incorporated a rubber mount in the lower part to absorb shocks and vibrations. I took off the airbox, kept the screen, and am using a #60 jet. The plug looks good, and the bike runs nice and clean with no four-stroking.
I discovered that the petcock was leaking everywhere, but I fixed it with a #9 faucet seal from Lowe's.
It feels great and pulls really hard in the midrange. Hopefully a 16mm SHA will help out in the top end. I'm calling this project a success.