Well, sadly, as the forum can only display one "default" group for each member, it's up to the donator to decide which one they want to appear as. They will still show up in the list of members with that user title when the group is opened, though.
I totally understand if people don't want to be identified so if that's your preference, also let us know.
The "Admiral's Club" doesn't confer any additional privileges, just a forum badge to indicate who has helped out financially with the project.
Well all that is fine and I do not have problem with that.
But what I would do is instead of using a "Admiral's club" color on our name, I would have gone for a logo or something similar, to show this is an member that help out financially on this forum. It could be a text saying: "Shipbucket financial contributor"