Yes, that's the one I was worrying about. I'm going to cut the holes and add a small fan too.
Curiously, I just put the 2445b up on the finished shelf and fired it up. (no holes yet)
A few minutes after I fired it up, she made a terrible sound and magic smoke came out.
I believe it was simply the Line RF filter module failing, which I've heard others describe here on the forum. Apparently, it gives this rather magnificent and stinky display of failure - and the scope keeps on working, though without (I presume) RF filtering on the AC line in.
Just a good reminder that these devices are not getting any younger, and neither am I!