If these are anti-banshee, I'd rather boost the HD. MM2 banshees have 26HD, but I'm willing to bet that 2e banshees had more like the 5 listed here. (As another reference, even the Paizo banshee from Pathfinder AP#17 is 14HD.)
That's it, though it's a fan conversion to the pathfinder rules. Funny, I tried looking for it on that site and didn't see it. Must have been too incorporeal.