Hello,
As the topic is Hung Ga's Lung Ying, and being a Hung practitioner from the Tang Fong lineage that just recently learned Tit Sin Kuen, I'm intrigued that most of the discussion is on Tit Sin Kuen. In the Tang Fong lineage (well, at least in the Yuen Ling, Ho Lap Tien and Lau Kei Tong lines), with regards to Ng Ying Kuen, our Dragon section is distinct and different from anything in Tit Sin Kuen.
My sifu taught us that our Lung Ying, in terms of overall movement, refers to obtaining a dragon-like body, with the emphasis on the flexibility of the waist and the ability to change angles and body levels in applying techniques. Hung Ga is known for developing strong stance and bridge; it is less-known that we also have strong waist. My sifu taught us that it is mainly from the Dragon that we get this ability.