If Dumbledore really wanted to keep the stone safe why didn't he just shove it up his ass? Maybe put it in a lined magic-safe bag beforehand, and then shove it up his ass so it will always be where he is so Voldemort couldn't get to it without facing him first. Heck, if he wanted to keep Harry's parents safe he should have just cast that huge space charm from HP4 on his ass and have the Potters live in his ass so he can always guard them.