I forgot to post this here, and it hasn't been mentioned:
xadmaster.library's internal LhA has a bug which shows up when extracting archives created with the new LhA - spaces in filenames are converted to underscores. A workaround is to use -H0 when creating archives.
The LhA client has been updated, MorphOS has the update already and OS4 users can download my externally-compiled version of the LhA client
here.
OS3 users do not have a fix as yet. Ideally, somebody needs to build xadmaster.library v13 for OS3; The source is available
here.
Chris