Well to answer ruler vs tape Q the ruler hurts when you press it into your pubic bone causing a wilting of the penis. Perhaps you may get accustomed to ruler measurements and get better results. Sometimes there is a space between zero and one” on your ruler.
Tape measures don’t irritate the skin as much I suppose that is why you get better results from a tape measure. You an get a root to meatus measurement which I think is more accurate for NBPEL. But a better BPEL measurement comes from a ruler.
Often time the tape measure stretches the inch becomes an inch and a quarter this will shorten you dick and shrink your girth.
Most polls indicate that 5”BPEL length is normal. And 4.75” is about normal girth. So 6.5 is a entire inch and a half above normal.