It would be great to get a forum type discussion happening for simulcast. The mailing list I guess is still sufficient.
What are you using to lock your RTCM's to 9.6MHz? If it's just the internal crystal still in there, then this is nowhere near sufficient, and will cause the audio to drift around like crazy.
You need some form of stable frequency reference that is the same between sites (i.e. GPS, OCXO etc)
I think from a previous posting the PCGM's had issues with creating a whole lot of noise and crud, could be wrong. Although mounting in a shielded enclosure probably helps. The board Joe came up with only requires a handful of parts and an OCXO.... he was also experimenting with the Leo Bondar programmable GPS unit, although this doesn't give out the 1PPS, so you'd effectively need two GPS units at the site.
The network I run on my simulcast system is via the internet, not via direct links as we don't have a path between sites. The internet is a business grade connection with low (<35mS) latency to the slowest site.