For dings and dents in balsa, before you add weight with epoxy and fillers, try raising the grain of the balsa. Its very simple. Heat up your covering iron. Wet the spot where the dent or ding is. Let the water soak in, then place your covering iron over the spot. The heat causes the water to expand to steam, pushing the wood grain out. When it dries in a few seconds, the dent will be nearly, if not completely gone. If there is a tear in the balsa in the dent, raise grain, then use a drop of thin CA to heal the tear (if there is a good fit).

Brad