Is it permissible to fast the third day as a completion of two days of fasting in the second half of Sha'ban?

Scholars have differed on the permissibility of voluntary fasting in the second half of Sha'ban, due to their disagreement on the authenticity of the hadith that prohibits fasting once Sha'ban is halfway through. The majority of scholars hold that there is no harm in fasting during the second half of Sha'ban, and that it contradicts the hadith: "Do not precede Ramadan with one or two days of fasting, except for a man who is accustomed to a certain fast, in which case he may fast it." As for those who rule against it, they see no harm in the fasting of one who has a customary fast.