The idea is to assign the EFC under one setup code, then switch to the other. Any such keymoves should stick after you change setup codes, as 3FG described. If shift-Power doesn't work for you, put it on some other button.

If he follows this thread, I'm sure he'll share those docs as well. I don't know where they are. Here are the EFCs for 30842 that I got from a SR702 user (prepend 00 to each):

180    input - MultiChannel
060    input - DVD
108    menu
104    display
100    return
107    setup
040    dsp - surround
103    dsp - all stereo
038    dsp - thx
036    dsp - stereo
115    dsp - pure audio
249    dsp backward
245    dsp forward
164    channel select
171    level down
167    level up
114    late night
110    Re-EQ
170    discreteOff

and for 30135:

058    input - Video1
054    input - Video2
056    input - Video3
002    input - Video4
057    input - CD
053    input - Tape
059    input - Tuner
055    input - Phono
183    vol up
187    vol down
184    mute
181    channel up
185    channel down
128    dimmer
232    sleep
191    up arrow
195    down arrow
188    left arrow
192    right arrow
130    enter
131    index backward
124    index forward
247    rewind
249    fast forward
120    play
118    pause
123    stop
245    record
164    dsp - direct
255    test tone
180    discreteOn
044    zone2 [prefix]