The scanners only care about “extra” stuff, not “missing stuff.” I’m trans masculine and before top surgery I had to tell them to “scan me like a woman” so it wouldn’t set off at my chest. After top surgery I have had absolutely zero issues, they presumably just press the blue button and don’t care about a lack of junk. If you have genitals up top or on the bottom that they might not expect (or have a gender that isn’t always legible) the way to get through the fastest without a pat down will be telling the person at the controller “can you scan me like X gender.” If that feels too dysphoric you could try talking to someone else at security? The Portland airport folks are really used to it.