My thesis is that flaccid length in particular tends to have a huge statistical variation in between individuals:
It’s all about how your cells make use of those polypeptides available to either create a surplus of elastin or a surplus of collagen in the course of the tissue healing process.
For my part, I did not do any ‘special flaccid size’ exercises at all, yet my flaccid went from 2,5”-3” to 5,5”-6,5”; erect is barely an inch more. I can hence conclude for myself that my tissue has a low tendency to rebuild cells with elastin, and a high tendency to rebuild collagen.
So I strongly question the claim that certain exercises would particularly aim at flaccid length. How on earth are these exercises supposed to make your cells prefer collagenous structures to elastineous ones?
You can surely do those ‘flaccid gain’ exercises as a psychological booster to ‘finally do something for ones flaccid hang’ - sure enough. On the other hand you might as well concentrate on a certain type of routine, either length-based (hanging, manual stretching + ADS) or girth-based (clamping, jelqing + ADC) to get the best out of your workouts. Once you get your tissue to a point to super-compensate the broken structures, you will gain, both erect and flaccid. Period.