The Phoenix/Firestorm team recently released a new beta version of FireStorm (v18.104.22.16815) which supports mesh. This version does not support uploading mesh.
The team was very reluctant to release this version but peoples demand for mesh forced their hand. There are many bugs! The Phoenix main page links to a list. Try this at your own risk, not every person will be effected by every bug. For me, search does not work at all, a blank screen. This probably is the result of my antivirus throwing out a file. Also shadows and invisiprims are conflicting again.
Most of these problems are in the LL code or in the way FireStorm must adapt to the LL code. Every one is working to get a full release version ready, but the team will not release crap! Give them time to do their jobs well (after all Phoenix/Firestorm is Built, Maintained and Supported by volunteers).