None of the flags are safe to use, it's really that simple. Neither are the variables. If you want to make them safe, that's a whole other kettle of fish.
Oh, they are stored in bits. Wow, I didn't even think of that. Thanks. It makes a ton more sense now.
Edit: I just came up with this in case someone finds themselves in need of more flags:
With it, you can choose which var you would not like to use and have 16 flags at your disposal.
(((Flag - 900)/8)/2)+4000= var number flag is stored in.
(I am not responsible for any bad eggs and such, check the var you want to use first:p)
You can solve for flag or var, just depends on which you want.