You have obviously been able to take his thickness---depending on his length, the next part is that if he is long enough, he may pass the deuadenum, the sharply curved tube that connects the large intestine with the lower smooth bowel (the part he has been in so far). Some people call it the "second sphincter". You will know when he penetrates that area, because it will feel very different. Some people like the sensation, some don't The main thing to remeber is that that the tissue in that area isn't as robust as the lower bowel, so can be torn easier. This can lead to a septic infection, which can be VERY dangerous and life threatening. Many guys are able to take and enjoy penetration in this area, but there are additional risks, and you have to be extra careful. Agressive thrusting while there can lead to tearing and abrasion, so if you want him there, be extra careful, and gentle. Good Luck!