Scott,
I use NCLink (free download, no spam) from OneCNC.net with a MC post set up to output programs longer than 900 lines.
RS232 Pin-Outs:
1 - 1
2 - 3
3 - 2
4 - 5
5 - 4
Start NCLink, open the .nc file (do not send yet).
Send Settings:
2400 Baud
8 Bit
Even Parity
1 Stop Bit
RTS/CTS Handshake on
Remove spaces UNCHECKED
Line delay 5 ms
Dyna Line Mode, Read/Write, Download, Program Execute. Display's Ready.
Go to NCLink and Send File. File transfers until line 900, machine runs, pauses while DNC downloads the next 900, etc. Works Great!