When I do pre-orders.... And after using pre-orders several times, I'm still not convinced it's any damn use... I only do Zon, Google Play & Kobo, i.e. those with whom I'm direct. The D2D requirements to have the final MS put up fourteen days out is a non starter, so no pre-order on Apple or the smaller retailers. I don't put any place holder file on Zon because that's where the f*ckups are most likely to happen. Since I only ever set up a pre-order once my MS is in my editor's hands, I have a product that's pretty final to use as placeholder on Kobo and GP. And as they recommend, I upload the final final at least 72hrs before release date. So far, no problems, but I haven't bothered with pre-orders on my last three releases because I found no upside and too many annoyances.