Hello Everyone, Trying to build a box for my av12. It will be an 85 liter ported. I put the values into winisd and came back with a 4" pipe 20 inches long. I thought it was a little big but went with it anyway. I ordered a 4" flared tube from PE and got a piece of 4" PVC from the depot. Murphy must have stopped by the house, cause of course the pvc and the PE tube don't match. Is the Winisd info correct and if so what do I do for a 20" pipe? I already cut out the hole otherwise I would be tempted to skip on the flared fitting. Any suggestions would be greatly appreciated.