My inlet is facing up and I do not have issues with air/cavitation as long as I am patient and let the air escape before turning on the pumps. Once in a blue moon I might have to manipulate the hoses a little to get an extra burp, but it is rare and not an issue. Only times I have had cavitation have been when pushing boiling wort through without applying patience to let the air work its way out. Air usually works its ways out in 1-2 minutes or less. Having the pump inlet face down would mean a bend in the hose of 180 degrees which I think would cause more of an issue, and is why I decided to go with inlet up. That said, I have not tried it so if others are doing it successfully, then it should work as well. My experience with the pump straight up, inlet(s) on top, outlet(s) at 90 degrees, works very well and keeps my hoses from kinking or pinching. Only thing you have to watch out for is trapped air, which will work its way out. The pumps will also help push out air as well. RDWHAHB!