My main issue with the Rambam’s approach is how he deals with the sifrei shelach source that seems to say that Beit Shamai holds that there is one string of tekhelet and three of white, and so goes the halacha. There is no source to my knowledge that indicates that there is 1 tekhelet and 7 whites. My Rabbi offered that he may learn Beit Shamai to be using the language one loosely to mean 1 half, for that was not his main topic, yet I find that fairly weak.
The sifrei is one halachic source but not necessarily binding – certainly the Rambam, and all who follow him on this (all Sefardi poskim, the Arizal, Radzyner, R. Hirsch, R. Zalman Nechemia Goldberg, R. Nachum Rabinovitch, R. Dov Lior, R. Herschel Schachter). There is no need to try to “squeeze” the Rambam’s position into, or out of, the Sifrei. R. Yehuda Rock, in his article on the subject in Techumin, explained that the Rambam is based on sevara, period.
– Mois Navon