One can locate the CG without any calculating. Rule: suspend aircraft from any point and theCG will lie EXACTLY below where that suspension line is theoretically extended thru plane. Perform this suspension from 2 or 3 different places to create an intersection point and one will have established the true CG of that plane.
Sounds easy but it isn't. Notice the true CG must be controlled not only along a wing chord BUT its height above or below lift point. Locate CG below lift point and one gets a very stable flying machine. Locate the CG above the lift point and one gets a plane that would rather fly inverted. Put lift an CG together and "hang on to your hat."
This will answer your questions re: dihedral vs flat wing. Dihedral simply raises lift point above CG and adds stability.
Glen