I have some 1.5 ohmn,1.8,2.2. I just purchased a Protank Mini2, it came with a 2.5. The 2.2's are real short and the tubes have a small diameter hole, smaller than the 1.5 and 1.8's but the 2.5 is the same as the rest. I am confused if I was to rebuild these, does the length and diameter of the tube have anything to due with resistance ?