b0ooo, thanks for the clarity about using only one .fir at a time. This tip worked for me but it works only about 50% of the time for some reason. There is no "Keep Magic Lantern" in the Format menu so I did lose ML twice before the light bulb went off. Well it's a beta so maybe beta 5 will have that feature? This is a good thing for the 5Dc and I appreciate all that have put time into it. Will donate when it's out of beta for sure. 