The thing that concerns me about this proposed change is that the poor programmer may look up the CLHS and see that the default value is specified to be 'single-float.
If anything, I'd say that ASDF should force standards compliance, and use 'SINGLE-FLOAT. But I'd rather have ASDF just leave this alone. CL is a language with side-effects baked into it. It's not our job to fix all of them: if we don't like that, there's always Scheme, Clojure, or Haskell. Note that we can still tell the femlisp maintainer that we don't like what the library does and ask for it to be fixed, without feeling that we have to go out and break applications that use the current femlisp behavior, or that assume that floats are read as single-floats by default. To add to the concern about breakage, this pushes more complexity into ASDF....
