Just got mine today as my first bottom feeding coil and did a pretty good build on it the second time. First time was normal coils, 28g 3/4 2.5mm silica. It was alright but I decided I might as well do micros. 28g 8 wrap with cotton. I didn't cut the cotton flush. I did cut it enough so that it'll pretty much cover the chamber so juice won't leak in. Perfect for now so I'm hoping I won't run into problems.