The key word is FILTER. That is what filters do, they filter out light and if all the green light has been filtered out by one filter, adding a second filter to try and filter out some more green light will make zero difference except increase print time due to added filter density.
Originally Posted by piu58
The question is whether all the green light has been filtered out by one dichroic filter. Possibly not but it really depends on your particular enlarger so adding a second filter may have an effect but not nearly as much as you might at first think.