From what I comprehend from this, you can only go up to your max health, therefore no. In a way this makes sense though, as it might be too powerful when you can do like 400 damage in one shot.
Before you could just pump up mass hp spells, spirits, items, get reduced to under 100 (from 800-900) and then pump it in a spell range, when enemy comes by, thus vaporising him for 500 ...but it is fixed long time ago
hey conker I am looking for the page that explains the intristics of using GB with runes I think it goes based off of your current hp not your "real" level 20 hp I do know that runes on your armor affect the spell drastically tho...