NavMicroSystems,
Did you keep the RX PIC's output at the same 4800 baud or did you speed them up for sending the data to the combiner 16F or 18F PIC?

I was thinking of bumping it up to 9600 just so the receivers would occupy less time transfering their data.
Did you also run all the PIC's from the same clock to save parts?
Regards,
tcbcats