OW loves doing this to me and after it grows a little, switches to inside. She doesn't like me to rub her outside the panties though. Says it wears out the material.

I haven't rubbed through during a dry humping session, but definitely when I just let my fingers wander. Then I get into it and kinda don't care....until my finger goes through. Happens very often. =)

I guess crotchless is a solution, but that takes away from the whole situation. That part seems more mental for me. The thought of going through your panties because you're so wild to get to yourself you can't bother to take the time to take them off first. Or the scenario of just thoughtlessly ending up with your fingers down there and then things just escalate.... Just seems to up the ante a bit for me.