Well, I have tried with all of them and changing frequencies but nothing improve, always same problem with high temps. Answering to your question, yes, I tried flashing 650 fixed frequency firm first and from there just swapping bmminer file for your file. For example, I have tried with bmminer 880 and frecuency 650 onwards, like 656, 662, etc till 762. With all of them I get same problem. Thanks for your help !