> Some can be considered obsolete in the R7RS world. Besides, having a
> number of cryptic extensions seems the least problem to me.

R6RS is not going away any time soon, and they are already using `.sls`
and `.sps`.

> Think of .c .cc .cpp .cxx .h .hh .hxx .hpp and another bunch of
> extensions telling you whether to preprocess the source or not, etc.
> This is the least problem with C++. :)

Just .c and .cpp would be fine. Perhaps add .h and .hpp :)