So depending on your needs and level of arousal, you can choose accordingly,” says adult performer and sex educator Jessica Drake, star of Jessica Drake's Guide to Wicked Sex: Foreplay. “If he's a larger size, especially in length, remember that most positions you're in - spoon, doggy, missionary - the higher up the woman's legs are, the deeper the penetration. Size does matter - in that it dictates how you play the game. You may think that size is your best asset, but it doesn’t necessarily offer a one-way ticket to great sex.