I don't want to frame it and I'm not worried about damage to the poster itself (more worried about damage to the wall). I'm mostly interested in glue/tack solutions but every time I've used sticky tack / blue tack it's ended up not sticking terribly well and when it does work ends up looking a bit lumpy. So, is there some kind of glue solution that will put the poster flush with the wall, and still be safe/easy to remove?