Support for header compression or ASS/SSA subtitles has nothing to do with any PMS clones. It is feature/bug of MEncoder builds.
Older ones doesn't have ASS/SSA subtitle problems but doesn't support header compression.
From opposite new versions support header compression but not ASS/SSA subtitles.
Only solution for now is to disable ASS/SSA tick box in PMS with latest versions so you will benefit with header compression and subtitles will not crash MEncoder(still ASS/SSA features as better antialiasing etc. will not be supported)
