Isn't the simplest way to answer that question. 

1. Draw a line on what is considered a whale. 
2. Calculate the total upvote stake weight, then subtract the amount contributed by those accounts above the line considered a whale. (This is the amount you must effectively downvote)
3. Apply a definitive downvote equal to the amount worked out above.

/edit 1

There need not be any subjectivity if we are to achieve desirable experimental results. 
Experiments must have known and controlled parameters so that we can test the variable(s). 
It is my belief, that if we are to conduct this experiment properly, then the line must be drawn clearly, and downvotes applied correctly without subjectivity.