It is just monokote over a well sanded structure. I built the plane all in 1 piece and it is very strong. The servos I used are: 2 JR digital wing servos buried in the horizontal stab for the elevator, 2 Futaba digital wing servos for the ailerons and 2 JR9411sa servos for the rudders. For the rest, I used futaba s3001 and s3004 for the air controls for the gear and flaps ( these can be any small servo). The hinges are heavy duty CA ones and I used twice as many of them for each serface as in a normal plane. I also sealed all of the hinge lines with either blenderm tape or clear monokote. The flap design you see in the pictures in my innovation and I don't know how they will work yet. If they cause too much of a pitch change then I will leave them closed and install the speedbrake system as per the plans but enlarge it as the construction article says. I had problems balancing the plane due to the extra weight in the aft ( 4 extra servos+ flap install) and I added a 3.5" extention to the front of the fuse just forward of the canopy to allow battery placement farther forward, even with this I have 2 oz of lead ( actually a 2 oz fishing weight) forming the nosecone! The plane overall is not too heavy though