In article ,
says...
There is nothing modular about
the Apollo spacecraft. The CSM is a matched pair always and forever.

Wasn't there some non-trivial thoughts about a light-weight mini-SM for
use with Earth-orbit missions like Skylab?
--
Kevin Willoughby lid

The loss of the American system of checks and balances
is more of a security danger than any terrorist risk.
-- Bruce Schneier