Angelina well, those would have been things i'm sure my dad could have told me too, if he wasn't going through the whole thing with a poker face.
Not sure how tight the tube on your dad's belt is, but cages can get really compact. There are even models that push the penis completely inside the body, though they are generally not considered wearable for weeks at a time. Not because of their erection-inhibiting effect, but because it is difficult to line up the urethra and to clean certain body parts.
Most pictures of full belts I have seen seem to have quite generously-sized penis tubes, which should be able to take some swelling before they make themselves noticable, and only really become unpleasant when it cannot help but... stand at attention.
