Assuming that we drop versioning, ambiguity comes from three sources:
(1) multiple search paths, (2) IMP.sls extensions, and (3) implicit
main naming convention.

I think the SRFI should just say that search paths are searched in
order, and within each search path, IMP.sls is chosen over generic
libraries.  The SRFI should leave (3) unspecified and leave it up to
the users not to have both "foo/bar.sls" and "foo/bar/main.sls" in
their directory structure (having both serve no purpose anyways).

So, I (as a user) should be consistent of whether to use "main" or not
for a library file.  If I choose it, then I name my files:
   foo/bar/main.sls
   foo/bar/main.ikarus.sls
   ...
and if not, then I should use:
   foo/bar.sls
   foo/bar.ikarus.sls
   ...

In no way should I name my libraries like:
   foo/bar/main.sls
   foo/bar.ikarus.sls
or
   foo/bar/main.ikarus.sls
   foo/bar.sls

I think this simplifies both the specification and the implementation
at the minimal cost of leaving the anomalous case unspecified.

Aziz,,,