There is a kit out there some where for this plane. I forget who made it. Long OOP. Yo're lucky to find one, if you want to sell LMK
The "CG" would be the same as any other plane.. most likely on the main spar if the wing is built up construction. Or 25-32% MAC
Look here for CG help
What do you mean by "End plates"? you mean Winglets?
Good luck