thats the way I usually do ports but round them over with a bigger round over bit at least inch and a half radius. the 90 you can get in a larger sweep then that and it is better on the air plug created. to hell with slot ports they are noisy. I just broke my old router about 30 minutes ago rounding one over. I needs a new one now. I start by mounting the pvc in the inner part of the wood but mounted halfway into it. then after I attach it to the baffle of the box I drill a quick hole and finish it with a flush cut bit then a huge round over. I don't know how you guys even compete on prices in this forum I cant do anything as cheap as all the people on here.