That's good, i didn't want to steer anyone away from experimenting, but stacking polarizers was a def no go.. and from our experiences, neither are vari-nd filters... and sadly that leaves one with single stop nd filters. I recommend you get a 2 stop. which is good and another stronger nd filter (not recommended for color, even lee big stopper has a disclaimer on it's website) for several minute long exposures which are fun. just my 2 cents.