Geng Jak Ging starts at the very foundation and doesnt need a specific form to develop it. There seems to be little to no concrete knowledge about Mang Fu Chut Lum and thus people attach things like that to it.

Train and understand the "4 ends" and "6 forces" and you will understand not only Bak Mei but kung fu. Its not about taking the chi to the furthest points from the dantien, its about getting the chi to leave the body! 4 ends is about propagating chi to the 4 conduits for that purpose. 2 ends of the spine (top and botton) and 2 ends of the spinal branches (hands and feet). Think about it and you will disagree, do it and you will see that its true. Theory must be derived from proper practice and dedication!