I do not own a hoyday-glider and the model is about 20 years old. I am not sure if there is a manual available anymore. For the CG I do only have following recommendation. Try CG on the first third of the wing (about main spar position). You will probably need to add some more weight in the front of the fuselage, because LiPo-batteries are much lighter than the old NiCd-batteries. Make the glider a bit nose heavy. Later on You can move the CG until You feel comfortable with the glider.
Sorry for having not more information.