So I finally had some time to continue. I have made the holes for the fans larger 25=>29mm. The fans are OD 30mm. I made the mounting brackets and made a quick installation to start bench testing. Unfortunately I have to use a BEC to run the pump and the fans I had at home was 12v. I will get new fans for 2s or 6v, perhaps larger ones as well etc. The testing will tell the need.