I know you're joking, but....
That should go in the lying thread. I've been to the Reykjavik penis museum, know what Ron Jeremy claims (even met him once), and am still holding a grudge with the urology department from where I did a lot of grad school. So........
Prause, N., et al. (2015). "Women's Preferences for Penis Size: A New Research Method Using Selection among 3D Models." PLOS ONE 10(9): e0133079.
Mautz, B. S., et al. (2013). "Penis size interacts with body shape and height to influence male attractiveness." Proceedings of the National Academy of Sciences 110(17): 6925-6930.
Veale, D., et al. (2015). "Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15 521 men." BJU International 115(6): 978-986.
Long story short: most guys are average. Most women say they prefer very slightly above average. How in shape you are buys you some leeway.