No, I don't know this for a fact. But I'm 100% sure that I want implants there and not HA. I, like the OP, am convinced that you can't have that level of augmentation (5mm or more) with HA. At best you can hope for a very subtle result, at worst it will do nothing. Not to mention the fact that it is not entirely stable up there. Implants are much, much lower risk and potentially can give you a 10 times better result, especially if they are customized for you, and not the off-the-shelf type.