I have also used masking tape to mark the CG location on the wings. This way you can reach under the wing without a helper and once the tips of your fingers are on the edge of the tape, they are where they need to be, then just lift to check CG. If you were only slightly nose heavy, why did you add tail weight? Could you have moved the Rx battery more to the rear to compensate and checked the CG, before adding weight? But do agree the only way to perfect the CG is to fly it and make adjustments as required.