The stands I built are very similiar to the Ascend stands. I e-mailed Dave F. on this issue. He told me that it was unlikely that the empty stands themselves would create any resonances- but on the other hand, if I was still concerned, to go ahead and fill them. I would think that if the stands were filled clear up they would be EXTREMELY heavy. Mine are still empty and are probably going to stay that way. I would think that a thin isolator pad between the speaker and the stand would do about everything needed as far as sonic benefits.
Randy