I did some tests yesterday, and my conclusion was that any Color Profile other than Canon's Standard (the default one) isn't reliable for UniWB+ETTR. I tested Standard, Neutral, Faithful and Technicolor Cinestyle. Technicolor is the flattest of them, making green and blue clip easily if exposed to the right up to the limit on 7D. Thus, the worst in this case. Neutral and Faithful were close to RAW histogram, but still not identical.
Standard reflected 100% of the histogram on camera LCD, being the best one.