When I sert up my Tiara 2000 (20'-2") I put a center rigger on her. After the first season, I took it back off. I just did not like it there. It was a pain to set, and got in the way when netting fish. The first time you try to bring a fish in between the out down, and center rigger, you will not be happy. It is easy to run a center rigger on a straight inboard, but with an IO, it is just to far back. Keep the back open for netting fish.
and just imagine how a Center rigger would be in the way ( the swim deck was not there when we had the center rigger)