I would be concerned about him holding it as well. I had a 3 year old dcb who started to do this when he was toilet training and we had to put him back in pull-ups and let him poop in them because it is very unhealthy for them to be holding it and can lead to problems such as Jennjubie mentioned. It sounds like it is a security issue (my 2.5 year is also unable to poop on the toilet so far, so I have to keep her in pull-ups) and more pressure may just make it worse. Personally, while I agree that he is way too old for this and should be trained...I would put him back in a pull-up for now before he ends up with bowel damage from holding it.