If you are able to move things around such as the battery mount location, this is always preferable. The further from the CG point you add weight, the less you will have to use. The heavy spinner is a good place to start, then add more if needed to get to the 28% MAC for initial flights. Make the weight easily removable because I think you will want to mave the CG aft slowly as you get used to the plane. Remember that this initial CG is a static one to get you going. After that you will determine the dynamic CG that the plane flies best with and that is a personal preference. It should take a slight amount of elevator to maintain altitude when in inverted flight. Another way to check is to roll 90 degrees and let go of the sticks. If the nose pitches down, you are nose heavy. My planes end up being at 30% to 32% MAC.