Thanks for the input everyone.
Filled up again this morning and guess what? Back to 42mpg.
Here's my best guess as to what happened over the last 8 tanks (approx.)
Went for a 500 mile ride with slower bikes. Holding back on the throttle yielded 50mpg.
Went for a 600 mile ride alone. Most of it was in higher elevations. 50mpg.
Went commuting. Bad math, wishful thinking, or failure to calculate my receipts means I thought I was still getting great mileage. Wrong. 42mpg.
Funny. I've always gotten 42 and it has never seemed to matter how I ride, even 2-up.
Feel free to pile on. It's Friday.