yes, 1 RM and 2x BRM's (backup RM's) and one field marshal. Field marshal gets a bonus pp like the RM's and all you may fly a DN. However, should an RM wish to give up his right to fly a DN, then he/she may appoint another player as a field Marshal to fly it for him.
The Hydrans and Mirak share a shiplist, which means they may fly EITHER OR race but not both in one fleet and may NOT share fighters. No Hornet III's on a Mirak ship, hehe. They will however have seperate RM and ARM's, as they are 2x races. It would be unfair to limit them just because they share a shipyard (which is punishment enough, dont you think?).