So even though the intent of this profile widget is to display an avatar, the developers of Sitefinity never bothered to think that a 4000px wide photo probably shouldn't be used as a avatar after 6 major iterations? Christ. Don't worry. Yet another custom hack accomplished what should be common-sense (i.e., out of the box) functionality. I wrote an extension to get the URL of the thumbnail (.tmb) file.
Sorry to vent but, c'mon. Not blaming you personally, of course.
BTW, your fix merely changes the dimensions on the client. A 4000px, 10+MB image could still be downloaded, but resized in the browser. Obviously on mobile, this is a terrible experience.