I seem to be sinking lower and lower.

As Dan mentions, we happy few in the Common Lisp world seem to be working at an absurdly low level. I mean, OK, we're compiler implementors, but the three previous sizeable improvements to SBCL from the pair of us seem to be better stack exhaustion detection, better floating point exception support, and correct undefined-function handling on the PowerPC platform. You will observe that those patches are mostly not touching any of the 100kloc of the Lisp code in the implementation.