Thrown incorrectly, the high cut with the longsword can leave you terribly exposed. Here are some suggestions to make the high cut a but safer and more effective. (And yes, I do realize that #4 and 5 are contradictory. If the masters agreed, we’d only need one manual.)

Step with your cut so you remain balanced. (di Grassi) Step with your cut so you cover more distance with your blow. (Cod.44.A.8) Step offline with your cut so he can’t counter you with a thrust by simply by extending his blade straight forward. (di Grassi) Don’t lean forward as it exposes your head. (di Grassi, Ringeck’s illustrations) Lean forward over your front foot to extend your range and present a threat. (Meyer’s illustrations) Cut into longpoint so that if you miss you can immediately thrust into the face or chest. (MS I.33, Talhoffer) Don’t cut into a low guard as it will expose you for a counter attack. Alber is called the fools guard because you have to be a fool to assume it. (Meyer) Learn to cut by rotating your wrists rather than your shoulders. This will make you faster. (do Grassi) Don’t make an attack without the intention of making at least three more. Even if your first two or three miss, as long as you keep the offensive your opponent (Liechtenauer, Meyer, etc)

A lot of people are in love with the leaping oberhau, where they launch themselves at their opponent. Apparently it works in tournaments, but if you don’t win that first strike it leaves you in a rather compromised position. So I’m very much against using it expect under the most unusual of circumstances.