I am currently using a vv Nova which is highly reccomended. it vapes pretty well but it gunks up frequently. esp with high vg juices. it also sometimes burns the liquid and does not wick correct so i have to shake it up every two or three vapes to get it to wick properly. anyway i have heard bottom coil has better vape production and shorter wicks. are they easy to maintain. i read somewhere kanger protanks were good and other people say they leak very often. what is the best bottom coil to use or should i just stick with top coil clearomizers. any thoughts on this?