Hmm. It occurs to me that I do need something other than "go like a bat out of hell." Without another dimension, I'm still in spacetime. If you recall, God claims in my book that Einstein made up General Relativity as a lark while soused. Nevertheless, any alternate explanation for what we experience in spacetime is still limited by the upper limit of light speed.
So we're, back to the starlanes. I still need a stardrive to shift to the starlanes, where everything in spacetime appears as ghostly images. Besides that, there are no flows. The stardrive simply allows you to go like a bat out of hell, or distances are shorter. I can either force the traveler to circumnavigate massive objects or allow the ships to pass right through the objects, including stars. I'm leaning toward the former (circumnavigating), otherwise you could fly through black holes, too. If the object has substantial mass, you have to go around it. Will ponder what to do about smaller objects (pass through them or deflect/destroy them).