Hi Guys,
I think if you had 50 women answer this question you would get 50 different answers.
Size is not generally a deal breaker for most women, I have even heard of some women complain that if it's too big it's not comfortable. Being completely honest, two inches would probably not really float my boat, but anything that's average-ish is going to be fine. Also, from my perspective girth is more important than length (put the two together and this would be my personal preference).
But it's important to know how to use it too, just pumping away start to finish and groaning whilst rolling off, probably isn't going to get too many girls excited. Vary the pace, the thrust, the angle (angle is quite important) and be sensitive to your partner's non-verbal communications. If in doubt, ask?
As for whether a woman will orgasm from penetration alone, again, it's an individual thing. The statistics (lies, damn lies and statistics) suggest that only 30% of women can orgasm from penetration alone, the others will need some kind of clitoral stimulation too. Now you can get that from intercourse, depends on position and angle etc, but manual or oral manipulation is usually received very well.
Above all else, have fun, mix it up and focus on all the other important parts of your relationship and your sex life will be fine.
Love
swingingstories