The adjustable incidence would be accomplished pretty easily. I'd only need the top wing to be adjustable. I'll set the bottom wing in the stock saddle and zero the stab to that.

For the top wing, I will install some blocks of wood where the cabanes and inner struts attach to the wing. There would need to be a blind nut (6/32) installed into each block of wood. 6 attachment points on the top wing. 2 on each wing tip and 2 in the center.

I'd need a bolt with no head on it, but a hole though the shaft. The bolt will run up and into the block of wood thats buried inside the wing. The cabanes would be bolted to that bolt with another bolt and nylon lock nut.

Adjustment would be as simple as removing the 6 bolts from the cabanes and struts. Then twisting the 6/32 bolts in or out, depending on the desired incidence adjustment. It would be easy to turn all 3 rear bolts out to gain negative incidence. Then simply run the cabane bolts back through and lock them down.

I've attached a crude paint drawing of the type of bolt I'd need. The hole in the top of the bolt would be used to attach the cabanes and struts with a separate 4/40 bolt and nylon lock nut.

It might not be necessary to build all 6 attachment points in this manner. I might get away with just using 3 of them in the back of the wing. I could use those 3 bolts to move the trailing edge of the wing up and down.

2nd drawing is a side view.

3rd drawing is a rear view--looking forward at the trailing edge of the wing.