ah, thats it. I think it will have a noticable negative impact on performance.
There is a guy in germany who made a lot of tests about coolers with nozzles. he tried different nozzle sizes too. In his tests one bigger nozzle in the middle was always a very bad thing and did affect performance a lot. It is a little different setup so it can't be translated to every nozzlesetup, but i think in this case it is agood guess that the bigger nozzle in the middle will affect performance negatively.
Read about it here (german translated with google):
http://translate.google.com/translat...language_tools