Hi
I have built many dual rotor gyros with great success. Most of the info that you find pertain to single rotor. One of the main problems with dual rotors is rudder size. Because gyros fly slow, the prop provides most of the air flow over the rudder and the rudder has to overcome the drag caused by the rotors for the gyro to turn. I converted a one third scale cub to a gyro and almost lost it on the first flight due to lack of airflow over the rudder. The Cub has a wide fuselage which blocks the air from the rudder, especially during landing, when the nose is high. This is something to be aware of. With dual rotors, increase the rudder surface by 50% over normal and you will be amazed at the difference in control.

Before rotor blades became commerically available, I curved all my own. Start by marking the blade profile on the end of the wood. I used a hand held belt sander, inverted setting on a table for the coarse work. Using a pencil, put lots of marks on the wood and that way you can tell where you have sanded.

Good luck and keep the sand out of your rotor bearings. Lets see more pictures.

Phil