I'll tweak Stickslammer's advice just a bit. Always balance the plane level. You mark the wing where the CG needs to be, then move your battery pack around to get it right. "A little nose heavy" isn't very precise, and will result in a sluggish plane if you marked the CG location in the right place to start with. Every trainer ever designed flies stable at 25%, and most give you a better feel in the air at 26%-27%. So start at 25% since that's definitely safe, and ease it back until the elevator becomes responsive enough on landings that you can flare properly without having to keep power on.
The other benefit to being precise with the CG is that if you have a mishap and need to repair the plane, you won't have to go experimenting again. If you've written down the CG and throw settings, you'll be able to easily restore the plane and get it back in the air with no surprises.