May I suggest to use concatenated extensions?
so the model mymodel.ldr, when compressed, becomes mymodel.ldr.gz or mymodel.ldr.zip or mymodel.ldr.7z etc.
this way, the files can be normally opened using the normal compression programs.
also, e.g. the Windows shell will treat them properly.
your tool might recognize these double-extensions and directly handle them.
the second portion indicates the compression standard that has been used.
so the model mymodel.ldr, when compressed, becomes mymodel.ldr.gz or mymodel.ldr.zip or mymodel.ldr.7z etc.
this way, the files can be normally opened using the normal compression programs.
also, e.g. the Windows shell will treat them properly.
your tool might recognize these double-extensions and directly handle them.
the second portion indicates the compression standard that has been used.