I will tell my story about this.
My dick has been at three stages: 19.5 cm, 21cm, and 22cm (current). I have been with slightly more than 15 this far (24 y/o) and not much of them were when I was below 20, just a little few. They all could manage my size, some better than others, and I don't currently remember I touched that spot with any of them, maybe just when pushing really hard.
I did some PE and reached 21 cm (8.5"), and things changed A LOT for me. I fucked much, much more in this past year than in all the previous ones, and I actually began to hit that spot. It depends on the woman: my ex-gf was easily reachable if I used all my length and pushed just a little, which was comfy. Other girls, like a very tiny one I knew, could reach it with much less than my total size (I literally had too much dick for her, but she was loving my size). But, per example, my current fuckfriend, which is a shorty asian girl, wasn't easily reachable by my 21cm. I had to push to get it. Now with 22, I do it comfy by just using all my length.
The rest of the girls were easily reachable with 21, the only one I struggled with, was this one.
Probably there are deeper girls with which you can need a 23cm unit or so, but I don't think there are much of them. My experience tells that with 21 cm (8.5") you can reach the deep end of almost any girl, and with slightly smaller length, you still can do it if you use a good possition and push hard.
But yes, they usually love it and cum quite fast if you do it proper. When you push too hard, they get a lot of pain tho, and also if you excite that part for too long, they have a tough time having sex again for some minutes/one hour.
PD: I talk about BPEL length!