Both, my Fiance, and her mothers pellets stoves where hooked up and have been running with Only a straight pipe out of the wall, and the downspout vent. Neither have had the OAK installed, and these stoves have both been used for many years like this. The OAK is now installed on ours, as I've read about how important that is. So, my question is, how important is it to have the T, and 3' rise from the pellet chimney? These chimneys come out of the house around 6' from the ground, so my only concern, is efficiency. Will the 3' rise be better off, or is the straight pipe out the wall ok?