If you really want to get pic's of flying squirrels, a friend of mine found that by taking peanut butter and sticking a bunch of peanuts to a tree in front of a trail cam at last light, he used to check his cam daily, and it was in his back yard, he got tons of flying tree rats on camera that way
I used to do it in my back yard, but never set up a cam over it
reason you need to set the peanuts out at last light is, regular rats get to them first if you don't