Completely removed the use of "nonce" variable. Posts marked preview are now accessible by multiple anonymous users. There is no longer a 24hr time limit.
Public_Post_Preview used the option variable as an array to store preview state - genius! However, it's use seemed backwards with an empty item == preview true. This logic was reversed so: simple_array[,,true,,true] now means that p=1 and p=4 have previews. This also allows for the preview to be turned off by default.