I use the "external antenna" option, with the Zwave antenna mounted outside of the enclosures at the top, above the rack. Nice to ASSume what you dont know.
The "problems" I've had are with Zwave devices dying, having to rebuild the database, and the way devices sometimes "disappear" from programs when changes are made. Other than the 2 enerwave devices I do not have communications errors on the zwave side. Insteon is another matter, but that seems to just be a "pre-failure" symptom of insteon modules. As soon as I see an Insteon taking several attempts to "write updates" I know it's going to be dead within 1-6 months.
So on the Zwave 500 board I don't see an external antenna port...does that mean the option has been removed? So to run 500 I lose option of pre 5 firmware and external antenna, but if I keep 300 I can't run a "final release" v5?
What a nightmare it is to wade through all this.