ATMEGA8U2 Breakout and FTDI cable

I'd like to try to use the ATMEGA8U2 Breakout(from sparkfun) in conjunction with an FTDI cable for prototyping a USB-MIDI device. The idea is to have them both connected to a breadboard arduino or an arduino pro and load new code to the atmega168 with the FTDI while still being able to use the USB-MIDI firmware in the 8U2 without reprogramming or disconnecting it.

Has anyone tried this approach? Anything I should be aware of?