PMMA can have some indirect lengthening properties. Men with some ED from mental issues or anxiety due to size, can see an improvement in length because they feel more secure (or “Alpha male”) in bed, so they can relax and get a fuller boner.
This is anecdotal, but it can happen. Not because of the
PMMA physiology itself, but due to the mental boost and confidence that can help you to reach your true maximum
Erection quality.
Dr. C reported one case that is similar to this.