RE: Monocoupe 90-A 53" wingspan
I found the plans easy to work from. The fuselage is "stick built". The best way to get both sides the same is to build the 1st side over the plans, then put a piece of Saran wrap over that side and build the 2nd side right on top of the 1st side. The plans show a rubber band hold down for the wing. I modified mine and use 4 nylon bolts to hold the wing on. I used K&S streamline tubing for the struts with a hard balsa plug to connect the upper an lower part of the struts together. The lower part of the strut is epoxyed to the fuselage (re-enforce the inside of the fuse in this area with some 1/8" balsa) and the fuselage fillet is made from "Bondo" mixed with some micro-balloons then sanded to shape.
Be aware that
1. This is a "short nose, long tail" type of plane. That means keep EVERYTHING aft of the firewall as lite as possible, and even with that, you will probably need to add nose weight to get it to balance. I don't know what brand of engine is shown on the plans, but IT IS THE SHORTEST ENGINE I HAVE EVER SEEN.
2. If you are going to use glow power you will need to modify the firewall called out in the plans and scratch a new firewall for mounting the engine about 1/2 way between the original firewall and the windshield. The original firewall will need to have a U shaped slot cut in it so that the engine can sit in the U. The other option is to lengthen the nose of the plane (that will destroy the scale outline though).
The first build I did I put an OS 46FX in it. I also had to add 8 oz - 9 oz of lead to the inside of the cowl to get it to balance. The OS 46 FX was WAY TOO MUCH POWER for the plane (I had unlimited vertical at 2/3 - 3/4 throttle, plus I was afraid to use full throttle). This is why I went electric. I bought a long skinny lipo and cut a hole under the motor so I could slide the lipo forward. My lipo sits even with the front of the cowl. I had to add 1 oz of weight to the inside of the cowl to get it to balance. The TowerPro 3520 is even too much power. A 28mm motor will have plenty of power for the plane although you would probably need to add more nose weight with that motor. In the electric configuration mine weighs in @ 4 lbs 4 oz ready to fly.
Incidence is not shown/called out on the plans. I set mine at 0 on the main wing and 0 on the horizontal stab. She comes off the ground in about 3' - 5' at 2/3 throttle, but flys fine. I suggest keeping a little power on for landing (I cut the power just as the mains touch and start feeding in up elevator to plant the tail) and try to make your landings "3 point" to avoid nose overs (especially if you fly off a grass runway).
Hope this helps.