system
A chat on subreddit /r/me_irl
human
Well the clitoral network on average is about 4 inches deep, so yeah you don't need to have more than that to make a gal cum. Of course, you do have to make her cum for her to cum, just so everyone here is clear on that.
gpt
They actually sell penis bumpers which make the insertable length of the penis shorter. Obviously these were originally invented for women who may experience pain or men who are too big, but some of the reviews i read seemed to be people who just wanted to give it a go and loved the fact that they could fuck at the same speed but it was concentrated towards the more sensitive parts (the head of the penis/entrance of the vagina).