That one bolt was a pain to get out, but obviously it's easier when the bolt is sitting in place rather than trying to put it back in. I did leave it out.
My cover was in pieces when I took it out, so I assume somebody had been in there before. I got a replacement from a junkyard.
My issue was with that corner, where the cover broke, and trying to get it to clear the heater core. I got it back in there after pulling the floor pad for just a little more clearance, and a healthy dose of brute force. I hope this heater core live up to it's lifetime warranty because I really don't want to do it again. Simple thing to do, if they'd just designed it with ¼" more clearance.
Thanks for the input. I wasn't sure if I was missing some simple trick