Upon request, I made a video where I'm masturbating while stimulating the area where my vaginal opening used to be. The skin on my perineum is a little loose, so if I press hard I can 'insert' two fingers up to the second knuckle, and it feels really good. It also helps me get better erections. I'm sorry it's not very clear ; it's hard to take a good video where this area shows well, especially since that particular 'penetration' is much less practicable from behind unfortunately. I'll try and make a better one.