The lead punch should be delivered directly fron the on guard position without any telegraphy and should land infront of your nose at the opponents face. (Lee & Uyehara vol 3 1991)
The lead punch is a potent offensive and defensive weapon because of its advanced position - it is halway to the target.
The fist should not be clenched until impact. Relaxation will give both speed and power!
Every blow just shoots from wherever the hands happen to be at the momment.(Little Vol3 1997)