I don't know but I think it's possible. If you stretch bones you bear a constant force that hurt the bones and force them to heal in a stretched stadium. This is painful.
The same could be done with the penis. The problem is that the penis move itself, and there are high pressures in an erected penis. Also scar tissue has the property to contract. If you do it not long enough, your penis can shrink. If it's done to strong or the stretch force and the erect force combine to strong you could hurt the spongy body of penis and get impotent.
The safest way is to use Photoshop or something like it.
