I have a large projection screen that I need to install into a (seemingly) pretty stable concrete ceiling -- at least that's what I assume it is -- it sounds very solid when hit with a hammer, certainly not plasterboard! The installation instructions are pretty sparse and only talk about wall mounting, but there are 8 anchors supplied (interestingly there are only four fixing points though -- 2 either side), they are 40mm long and 10mm in diameter, made of metal and threaded for M10 bolts. I'm not an engineer, but I understand that mounting on a wall where the stress on the anchor is lateral is a very different animal to ceiling mounting where all the force is directly trying to pull out the anchor. My question is, would these anchors be appropriate for the job? Of course, being a projector screen, the dynamic force subjected to the anchors combined would be more than just the weight of the screen as it will be pulled down. I would appreciate any advice anyone has. Many thanks!