So basically, you can't use the long tube at all with only 1 18350 as it will hit the display, the long tube will wobble if you use it with a 18650, and doesn't wobble with 2 18350's. The short tube doesn't wobble with either 1 18350 or with 1 18650.
I had heard it said before that different devices produce differently, the taste from this SVD is rocking my world right now. I'm a believer, it is a superior vaping device.
I got a Innokin itaste SVD and Vamo V5 today from them. If they are not authentic, they are very good clones. The price I paid, I'm very satisfied. Just don't expect to get your stuff in 3 days, expect more like 3 weeks and you'll be fine.