Long and thin will get you in.I'd be interested in girth. An ex-girlfriend's new boyfriend once called me "pencil-dick" during an argument... He wasn't too bright, so it could have just been a name he heard elsewhere and repeated.. But it always stuck with me.. I've never been worried about my length (7.5 to 8 inches) but perhaps I'm working with a particularly skinny member.
But short and thick, that does the trick.
Then again, it's not the meat, but the motion.