My, how we guys can "conjure up" things to worry about!
I sincerely believe many of us could get the tape measure out every hour and find a different measurement!
--Then, we'd either find something to brag about or lose sleep over!
(WAIT ! Maybe some of us are doing that! ;D )
How about one of us being honest here, though and just state the obvious?
(I believe this is true for virtually any guy who is truthful)
Penis erect length (and girth to some extent) DOES vary(comparatively) during any given erection.
And, this variance DOES depend upon the stimulus, the occasion, even the duration time of the sexual "activity".
The larger among us will attest (no doubt) that the great volume of blood required to KEEP a firm erection is awesome. How can one expect the same erection quality over and over and over? Many of us have to squeeze and hold the thing just to get it to behave and be rigid enough to "enter". (I'm not by myself here! --I've read other accounts as well, --many of them)
My erect length can be about 1/2" SHORTER than the maximum erect size I actually list. Girth is more consistant, but it too can vary just a bit. In fact, when first erect, I tend to not have the TOTAL girth I can achieve until several minutes later and, often by that time, the length will then have perhaps diminished just a bit....Still, later on, the REAL maximum size ensues and then (I suppose you could say) things can suddenly become REALLY interesting!
BTW---Many of those photos we see on the websites showing these stupendous sizes (flaccid and erect)---no telling what "prompting" and "fluffing"goes on before the camera shutter snaps! Many of these same guys in day to day reality would be a disappointment (and a shock to many) who are trying to live up to the size standards being portrayed.
Point here, guys---is not to worry. It' s okay to be "off" a bit sometimes in measurement size.
As to the mention of Peyronies's disease, if a guy has this, HE WILL KNOW IT! Not only can the syndrome be somewhat painful; the "bend factor" is quite pronounced. I would think that erection size would then become the least of worries! Being able to cope with the inconvience of limited use (and again, often the discomfort) would certainly be THE issues in that given situation.