In the WYKKO, there is no canon with respect to the title of Master. The title of Shihan is given to Yondan blackbelts at some point in their training, before they can test to Godan. Titles like Fukukaicho, Kaicho, and Soke relate to the individual’s role in the organization, but do not equate with titles like Renshi, Kyoshi, or Hanshi which other organizations use to indicate mastery. The English title of Master is never officially used in the WYKKO.
When I wrote the WYKKO Handbook, I asked Masters Toyama and Culbreth about the use of the title Master. They both seemed uncomfortable, and agreed that this is a title that cannot be claimed, it can only be conferred. That is, an individual cannot attain a certain rank and say, “You should address me with the title Master now.” Instead, the bosses said that an individual is given that title by their students or others below them in the organization. Presumably, Soke could say that a certain rank of student should be addressed as Master, but he hasn’t done that to date (December 2015).
So, now we have a situation where the students need to be aware of when they can or should use the title Master. Technically, since the bosses say this is a title conveyed by the students, the students could choose to use this title when addressing any blackbelt. Within the WYKKO, however, it would be odd for students to address some blackbelts as Master. So, how can students be appropriately respectful and avoid a faux pas?
The easiest solution is to never use the title of Master. The bosses address each other (and everyone else, including Soke) as Mister, and most or all of the Shihan-ranked blackbelts also address everyone as Mister (or Miss). I insist on using the title of Master for two reasons. One, other styles use the title of Master, and I think it’s important to emphasize that there are individuals within our organization who have a degree of proficiency that one would acknowledge as Master. Two, I do feel that some distinguishing title should be used when addressing certain high-ranked blackbelts to distinguish them from other high-ranked blackbelts. The formal titles (Sempai, Shihan-Dai, Shihan, Kyoshi, and Kaicho) are not used in verbal forms of address.
If you want to use the title of Master when addressing or referring to a high-rank blackbelt, the only rule of thumb I have is my Sensei. Sensei Blanck would refer to Master Toyama _as_ Master Toyama. This was when Sensei was a Yondan and Master Toyama was a Rokudan. Everyone also referred to Master Koda as Master when he was a Shichidan. Therefore, I assume any blackbelt at Rokudan or higher rank may be addressed as Master. You may also restrict the use of the Master title to the Directors of the organization- Master Toyama and Master Culbreth.