I'm pretty sure Downing keeps in frequent contact with RDC, so you could try PMing him or leaving a comment on his blog downingsbasement.com. I'm sure he would be able to help you and RDC connect.
Ive programmed an arduino to replace the CNT-NUS chip.
It suports rumble.
You can use to use the N64 original or PS2/Gamecube style joysticks.
And it emulates a memory card with an eeprom. (untested, waiting on eeprom in mail)
I have tested this with rumble on an atmega328, atmega328P, and atmega168. All work great!