This post is for the next guy that tries to do this. A few things I learned:

- you can put a basic MAX232 on the TX and RX lines and "watch" what is being sent around your network.
- 4K7 pull-up resistors are good for master and slave RX pins (supposedly only necessary in case PIC is disconnected).
- a structured approach to communication helps, ie: a PIC address, a command, data and checksum.
- slaves then look at the PIC address and decide if it applies to them, a "calling all slaves" address is also useful.
- a local command can help support various processing.
- data can be as big as you need it.
- and checksum can be as simple as addition of every byte sent, a word variable has more room.
- RS232 is great for Master to multiple Slaves, as long as only 1 slave replies back UNLESS:

Code:
...
TXSTA.5 = 1                                 ' Enable USART TX function

HSEROUT (slave sends reply only when spoken to by master)

TXSTA.5 = 0                                 ' Disable USART TX function
...
There's more than one way to skin a cat, but this was by far the easiest to have more than 1 slave on the MASTER RX line. There may still be an issue with this solution, but I have 6 slaves sharing a master RX line right now and they're all purring nicely.

Thanks to all that helped me work through this (don't even want to count how many days it took to get this working).

Robert