As much discussion as there has been by reviewers and end-users regarding the Cornwall, you are the first I have seen who mentions raising them. I think it is not only desirable but necessary. The main horn should be at ear level when seated. I just bought a pre-owned set of highly modified Cornscalas, and I'm having a custom set of 8 inch tall walnut stands made for them.
It's my past experience with a set of Klipsch Epic CF4'S that having the midrange horn at ear level is critical. I have no idea why professional reviewers don't even mention this. I am also adding brass cones to each leg from Livevibe which even without the stand would make a big improvement.