I have recently modified my seat into a full-motion rig, still 2 DOF of course.
You can see a photo below. I have used two aluminium L-beams ( 40x40x2, length 850 mm ), mounted on the inside of the top rails of the platform. This extends the platform forwards and I then mounted a multiplex board in between. There is a slight angle downwards on the beams, so that it’s not completely jet-fighter style.
You have to be cautious of the clearance with lower part of the frame, so the beams need to be mounted inwards enough to avoid any conflicts. I used large washers for that. My frame is not completely symmetrical so it’s hard to give exact measurements for this clearance.
It all works quite well, the motion system does not really care about the extra rotational momentum it has to generate, movement is still very aggressive if so required.
The flying itself is completely different, you get fooled really quickly into believing your are gliding in the air in a box.
I did notice that the braking sensation - while taxiing for example - is a bit less, which is of course logical since I do no longer have the reactive force of my legs. Is that a deliberate mechanism used in the profile? To accentuate negative G surge forces less than positive G?
In general I had to boost everything to 1.6 to get similar sensations.