I understand you are just painting a picture with your example, but I honestly believe that there is a slightly bigger difference between having 11 rebounding and having 16 rebounding even if you are only comparing them to someone who has 9 rebounding (which I'm sure many div 4 teams have).
I think that now that he has the 16 rebounding player, he will certainly dominate the boards, and will give him more flexibility to play tactics such as a 1-3-1 zone and still maintain a strong rebounding rating.