Ever notice how, if you take your finger and place it right on the tip of your penis, even while maintaing the hardest of erections, you can press it in quite easily by about at least half an inch?
I would imagine that first half inch, she isn’t feeling too much of when your all the way in her,
it’s when it gets compressed a bit and hits the harder tissue of the penis, that she would begin to feel it,
and this is of course you hit her innermost depths.
Just food for thought.