Last I checked the dictionary meaning of Sneak = To go or move in a quiet, stealthy way.
But in Fonline 2238 Sneak = Invisibility because a high sneak char can walk up to you in broad day light steal from u or plant a bomb in your inventory.
I suggest that this should be changed, than every chars PE will have a chance to cause sneak to fail, example if u have PE=1, than 1 square sneak char will be visible. If u PE=2, than 2 squares, PE=3, than 3 squares up to PE=10 which is 10 squares.
Since the game dont really have terrain, vegetation, shadows that sneak char can hide, than this might be a good way to implement sneak, instead of current form.