T Hawk-4 reads, "First E: If this attack deals damage, add 1 Hawk token to this card. You may only play two more Enhances during this attack."
First sentence of the ability is an "If", so the entire ability is contingent on that "If", right? Does this mean we were meant to play Enhances during the Damage Step?
Lynx Tail reads, "E: This attack gets -X damage and +X speed. X may not be greater than 4."
The lovely thing about the wording of this is that it's completely unambiguous. X may not be greater than 4 => X may be any number less than 4 => X may be any number less than zero. Sure, it'll be really slow, but there's rare Raphael, Deceptive Quickness, and good ol' fashioned "no low blocks" to deal with that...