Just my opinion but I see no advantage to plugging the bottom air hole. It works well. I also see no advantage to putting the additional air hole on the opposite side. It is best, in my opinion, to put an extra hole in the same vertical line as the stock hole, anywhere from 5/16" to 7/16" above the stock hole.
I plugged the hole bc I was tired of having excess juice come out of the airhole, when I dripped some juice in it. Plus with the new drilled hole I can aim the airhole at my coil by simply turning the top cap.