Huh, I very rarely hear about people using Common Lisp these days. Or Lisp at all, outside of Emacs Lisp (stories of Emacs Lisp often being tied to their nasty core dump hack).
What are your reasons for sticking to Common Lisp?
50MB "runtime" sounds quite extreme, even in this day and age. That's 2.5x the consumption of a fresh Node.js instance on my machine. :/