I am a disposable only user (at least for now). However, I *nearly always* set off the detector at both courthouses and airports due to my metal hip joints. I have to admit that the pat downs I have received have been pretty lame. And so far I have *never* been asked about the bulkiness around my waist line; even when I was getting near the "full up" level. Frankly, I really am not worried about getting patted down at an airport!

Which causes me to wonder "how good is the security?"; especially at the airports where I sometimes do not set off the alarm!
As for DDS's question about why things get set off at times and not at others, that depends on how "sensitive" they have the detector set to. On a few occasions I have not set off the alarms when it was the same detector from the same location/entry point. It just depends on the security person that calibrates the unit at the start of their work-shift. And given the amount of metal I have in my legs, it makes me wonder what else is getting through!
And just to add insult to injury, a couple of years back I had fractured my knee so I was on hollow, aluminum crutches. Several airports & court houses just waved me through!

No pat downs or follow ups! For all they knew I could have been faking it! WOW!