From what I have gathered from my research on the subject is the following:
1) The number of neutered males does not matter.
2) Intact males tend to have dominance issues. Keeping two intact males together is not advised. Most successful intact male pairing tend to come from siblings born/raised together. (I have one of these)
3) If you have more than one intact male in a group or colony, it is not advised to introduce a lone female to the intact male pair as there may develop a dominance issue to mate.
4) If you introduce a lone female, it is advised to neuter one of the two males before the introduction.
5) If you plan to keep your two intact males happy, there needs to be a minimum of 1:1 intact male/female ratio. (But even this may not work)
6) Colony breeding is the only time I have heard of a dual intact male with females situation working on a regular basis, but that is a ratio of 2 males and 10-12 females.