Hate the breakpoints for HP 20 and HP 30 and healing? Annoyed that your HP 19 guy isn't getting anything until he finds 2 more points to spend?
Here is an easy option to fix that.
Round all effects down.
Instead of the rules for High HP and Healing (p. B424), use these:
HP <15: Healing is x1.0 effect.
HP 15-19: Healing is 1.5x effect.
HP 20-24: Healing is 2.0x effect.
HP 25-29: Healing is 2.5x effect.
HP 30-34: Healing 3.0x effect.
HP 15 folks, rejoice!
While you could just multiply all healing by HP/10, it just gets silly. The game has breakpoints - smoothing them doesn't imply the need to get rid of them. And it's easier to remember a few extra breakpoints than apply a formula per casting.
And for those you who say, Bah! I want more breakpoints! Well, Christopher Rice has you covered.