You check the Cof G with the wings on. I think that picture was posted for reference only. I normally check it with my finger also, and have the plane at about chest level with the prop facing me. Just adda mark wherethe CG needs to be with a marker or something, and put your fingers on those marks. If the tail drops, its tail heavy, and if the nose drops (very unlikely with this bird) then it's nose heavy. Then add weight accordingly.