Currently, there is no safe way to do this with an erect penis. However, if your problem is that it looks too small when flaccid, then Viagra will make it hang lower by virtue of delivering more blood flow to the penis. Some pumps claim to add girth, but not erect length. Look up jelquing which is a stretching technique--there are videos online. Once again this is mainly for flaccid penises that shrink up too much and need to hang lower.