curved ports vs. multiple ports

Hi all!
I'm constructing a ported enclosure and have the following problem. To achieve a port which is large enough in diameter that it does not "whistle", I have to make a port that is longer than the largest measurement of my planned enclosure. So, I was wondering if it is better to use an elbow with a single large PVC port, or if it would be better to use two smaller diameter ports that would fit in to the enclosure outright. I've heard that bent ports can change the dynamics and general operational characteristics of a port. If making a curved port, is there any special design tricks or considerations for making them work best?

Cheers all!