I have built acceptable RingMasters, P-51, Jr. RM. Neuport 28 , Yak from sterling kits. Place the die cut sheets face ( printed side) down on some sandpaper on a flat surface, snad with 120 grit on a block to clean up and thin the sheets.
The wings will build pretty straight if pinned flat to a board from the back of the spar to the trailing edge, and support the front of the ribs wth a straigt dowel or piece of tubing to keep the leading edge straight.
Sand the heck out of the fuse aft of the wing, back to the stab platform, the drawing shows a cross section tapered at top- rounded on the bottom and wth the thickest part at the wing centerline.
Many people extend the engine bearers farther back for increased rigidity, if nothing else add a piece of hardwood between the bearers at the wing leading edge, and use plenty of glue on he bearers and doublers.t
Finish it, fly it, and try to stop from smiling.