An UPDATE
The ranks of O-parts is from E-S (we're excluding SS as Shin is the only SS rank O-part, and will be the ONLY SS rank O-part)
The Ranks of O-parts are sensitive things. We admins will probably assign the O-part rank. You can suggest one and we will give our approval if we deem that the rank is appropriate, but will suggest what we think the O-part rank should be if we don't agree. Most likely, (whenever he returns from what he is doing) Dee will probably approve of most of the O-parts, for the time being I will be.
Please remember that the rank of the O-part must be in range of what your rank allows. This is just to make things fair. You can reserve an O-part if you suddenly are hit with a wonderful idea of an O-part, but you will not be able to use that O-part until later when you get to that rank.