I never tried needles. In another thread I mentioned that I went through a "Try new things" phase. There was one particular mistress who was very important in that phase discussed with me a list of things she hadn't yet done to me but wanted to do. Some of those items were performed but needles was on my "soft limits" list which means something like, "A day may come when someone will do XYZ to me---but not this day"

I have experienced single-tail but only 4 times IIRC. Mixed results

In my reply to Mistress Ayn I said that some experience a deeper in-session subspace than I do. You are one of those