Final thoughts:
Chuck Cunningham did a great job of designing this plane.
The plane flys great even though I had to do some "bashing" to get the CG correct. I really hate to add weight to an airplane to make it balance correctly and none was required for this one.
Coroplast weighs over 2 oz per square foot which makes the tail really heavy compared to the normal materials used for model planes.
I don't have the manual dexterity to deal with a bunch of 4-40 bolts and nuts to mount the wings and rigging, so the bottom wing is held on with four 3" x 1/4" nylon bolts. The top wing is held on by four 3/4" x 1/4 nylon bolts. The cabane struts are held on by eight 3/4" by 1/4" nylon bolts. The two interplane struts, one on the right and one on the left, are held on by two 3/4" x 1/4" nylon bolts, one for the top wing and one for the bottom wing. Yes, I did buy the 3/4" bolts by the bag of 100. I have holes for the rear interplane struts, but since the Coroplast wing is so rigid, I don't use them. Wing mounting at the field is quick and easy.
The major change, which also affects the looks, was to move the top wing back four inches to get the CG on the right spot. One thing that is interesting is that there is no CG change with the top wing on or off. I could fly it as a monoplane, or a bipe. Of course the wing loading would be pretty high without the top wing. I may try it later just for kicks.
The other change, which is minor, was to add about 3 degrees of down incidence to the top wing. That was to help with the slow speed flight. The top wing will stall shortly after the bottom wing. Since there is no sweep to the top wing and no stagger, I felt that it would be wise to make that change to prevent a wing drop at low speed.
I was a little concerned about the "lifting tail" design and saw that some of the people who built the plane decided to just use a flat stab or a symmetrical airfoil. The choice does affect how the plane will behave with throttle changes. I put in about 2 degrees of right engine thrust and 3 degrees of down thrust. With that set-up, as I added throttle the plane did not climb at all since the tail provides more lift which keeps the nose from pitching up. With two huge Clark Y airfoils they would provide a lot of lift as the airspeed increases, so Chuck made a good design decision to have the tail airfoil so some lifting to keep the plane from pitching up too much as the speed increased. I don't need any trim changes from 1/4 to full throttle. I could have used a little less down thrust on the engine to make the plane fly more like a real plane.
There is a lot of drag with this design, so there is not much change in speed from 1/4 to full throttle, and just noise change from 50% to full throttle. The plane is "lazy" in the air, it just seems to float along. It looks very realistic.
Takeoffs are a little tricky due to the short fuselage. Slow throttle inputs and fast rudder inputs are required to keep the plane straight until a little speed is built up. I think that may be why some people have increased the size of the moveable portion of the rudder. I added 1/2", it could probably use a little more. I also took out all the rudder expo that I had initially. The plane will be airborne before you know it.
Landings are great, the plane comes in like it's on rails. Due to the weight, a little up elevator, to stop the sink rate, is required a little earlier than I'm used to. I'll get the hand of it after a few touch and goes.
If I were to build another one out of Coroplast, I'd lengthen the nose a couple of inches and leave the wing stagger alone unless it needs to be moved to change the CG.