Peter North's limp dick is actually not small. It is probably bigger than most. It's just a lot smaller than you would expect if you have previously only seen it hard.
He is not the only grower in the business. I have seen John Holmes appear in a scene with his dick initially completely soft, and believe me, it was not an impressive sight at all. While it was of above average size, it was a pretty feeble-looking little thing compared to what it grew into. The same goes for Mandingo. (There's a thread about him being a grower.)