The combination of BHT and sodium citrate was the best in Dunn's tests. However BHT + EDTA and ROE + EDTA combinations were also very good. Even though I no longer sell soap, I always think of it in terms of a product anyway, so I switched to ROE + EDTA because BHT has negative connotations for people from its use in food. A concern about BHT in soap is, of course, ridiculous, but we live in a time of chemophobic faddism and deep, willful ignorance.
Previously I used BHT + EDTA with good results. I retained samples of the soap I sold, and it was a good 7 years before I noticed a color change from oxidation, but never any spots. However, ROE + EDTA was pretty comparable in the Dunn experiments. I never tried BHT + citrate.
There is one additional odd thing about BHT that spooked me a little, but I don't know what to make of it. A friend of mine at my suggestion tried the BHT + sodium citrate combination in her HP soap (she already used citrate but added the BHT). Her batch turned vivid yellow in any test she did. This is apparently the color BHT turns when it's antioxidant properties are exhausted.