What would be the smallest size penis girls would feel pleasure?

Men do care much more about the size of their penis than women do (see ian kerners book "he comes next"). It is a known fact that women are only able to feel about the first two inches inside their vagina. So as long as you are at least that long, she will feel you. Women generally enjoy the feeling of penetration but most cum from clitoral not vaginal stimulation. Don't be more concerned about the size of your penis then you are about enjoying the experience or making sure she enjoys the experience. Nothing is more sexy then confidence. Mind blowing sex comes from your big head, not the little one! Pay attention to the signals she's giving you. If everybody is having a good time, does it really matter what size you are?

I'm pretty sure it depends on the girl, but personally I'd say 5 inches to 6 1/2 in length are reasonable sizes which also seems to be the norm.

She only feels the first 5 inches

Probably anything less than 4-5 inches is pushing the luck. Anything 6 or above is pretty good.

I heard as long as its longer then 1 inch she still feels pleasure.

To be honest, I think guys care more about dick size then girls. I'm about average, about 6 inches or so hard, but small when not hard, like two inches or so, and I've never had a girl complain. I've never had a girl take a second look, and I didn't ever get the feeling that they were disappointed. It's all in how you use it anyway I'm pretty sure, but if the girl likes you, then it matters even less in my experience. Also, think of it this way, if you have a small cock, it makes your balls look bigger! I've come to terms that I ain't the biggest guy in the world, but f*** it, I still rock out with my c*** out. Point is, I wouldn't worry about it.