Cool... I guess it is a sort of stationary version (i.e. legs don't move) of piquan then?
I have seen stationary versions of the wuxing (at least one for each; sometimes more); maybe these would count as part of the 18 neigong in your system? However, I am not sure if every Hebei xingyi system has these or not; some may have just concentrated on the wuxing (moving) and working on the principles in there (maybe Sun Lutang's and Li Cunyi's styles?).
I guess I am not sure what would be considered a neigong and what would be considered a technique...