There isn't anything super special about a two place dominator.
If you take the single place dominator, the two place is scaled up. The single place turns a 60 inch prop.... the two place turns a 72 inch prop.
To do that, the landing gear is longer, the tail is taller, the mast is taller, the front landing gear is longer.
Depending on the intended engine for the gyro, it would be built either " Heavy " or " light " by this I mean the mast might be made of a 2inch by 3 inch stick of aluminum, for the heavy gyro and the light gyro might just use a 2x2 inch stick.
Rotor flight dynamics was around since the 1970's. Maybe even before that. Ernie Boyette had seen the gyro plane hobby go through its most deadly phase. Tons and tons of accidents and deaths. Even to this day, when you bring up the word gyroplane or gyrocopter to folks who have been in aviation for decades, they will look at you funny and think your stupid for wanting anything to do with those " Deathtraps " They think this way because of that terrible period of time where so many people had accidents and or deaths in gyros.
It's one thing to offer plans or even a kit for a single place, and someone shortcuts the build process... or shortcuts the training process... or just goes out and makes very poor flying / pilotage judgment and they kill themselves. It is a whole other situation when the machine has two seats and someone not knowing any better hops in that back seat and is also killed. That is why even though the dominator is a very safe design, Ernie never wanted his machines duplicated by just anyone. He wanted control over who could have a two place. He wouldn't sell you a kit, plans, or even a completed machine without you having documented time and experience in single seat gyros. I think he wanted at least 150 hours time in type before he would consider selling you a two seater.
If anything you have to commend Ernie for putting safety over dollars.
So saying all that, you could " Copy " a two place dominator.
One of the things that makes dominators fly the way they do, and handle the way they do, is the following
1. The position of the thrust line in relation to the rest of the airframe.
2. The tall cruciform tail.
3. The additional degrees of travel the rotorhead has in pitch and roll ( most gyros it is 18 degrees each, dominators are several more )
4. The geometry of the controls, Long travel ( stick moves a lot more compared to other gyros ) makes for easier control / light stick
5. The main and nose gear having some suspension, allowing a cush ride over turf or other less than ideal surfaces.
So as long as you duplicate the over frame dimensions, use dominator type tail, duplicate the rotorhead and control assembly and use some means for suspension you can have a gyro that's going to fly very much like a dominator even if it isn't.