right on ! but if she sits on him a 4" tool will be a 5" tool.
physically the woman doesn't sense contact much deeper than an inch or two.
thrusting contact with the cervix she can sense. he might never reach it, she might not mind if he doesn't..
there are many contact sensors around the sphincter cunii (sp?) (muscle) just passed the vaginal opening..but they are not present much farther in.
not a professional, not trained, disclaimer, disclaimer.