I left a review on Etsy once of a pair of ice silk briefs with an open ended cock sleeve, with a photo of me in it fully extended to show the briefs in action. Kept getting messages after from guys complimenting my 'review' and asking intimate questions about how I was finding the briefs. Sadly...
I guess the perfect size is in the eye of the beholder. I'm a grower, about 2 inches soft but can grow to about 6 inches when fully erect...I've always felt quite self conscious of it's small size when soft but it's never not been enough/too much for others when hard.