A collection of posts by David Weber containing background information for his stories, collected and generously made available Joe Buckley.
Does the transition have to be made under impeller drive or Warshawski sail, or either?
Outside a grav wave's area of influence, you do not necessarily have to be underway to make a hyper transit; it's just a little safer because the forward movement gives you more dimensional stability when you crack the wall. If, however, you are making transit into a grav wave, you must have rigged at least one set of Warshawski sails, or grav shear will destroy your vessel as you enter the grav wave's area of influence.