[Steve_Alaniz]

The HELP section of the Stamp editor program has a built in manual and you can access the example drawing at the end of the SERIN or SEROUT command explanations. They mention that to protect the stamp from the higher RS232 voltage levels you need a 22K ohm resistor to limit current. I don't see that on your diagram but the stamps are pretty robust. I'd add if you continue to use RS232 but I believe you can just go straight TTL.
According to page 11 of the RC reference guide the port2 is TTL but since IFI FIRST doesn't support the using the serial ports there are no examples. Anyway, my read on port 2 is that you don't need a serial converter and should be able to connect directly to the RC controller.
The example for the stamp shows a pulldown resistor. This implies some kind of open drain output and may be a problem in your setup.
I have a stamp laying around here. I may set this up and see if I can get a stamp and the RC to talk later.