Not real well.
Rather than trying to describe the failure with photos I made a video, that is unedited, to show the failure.
CLICK THE LINK BELOW TO SEE THE VIDEO:
Seacock Failure Test #1 VIDEO LINK
The thru-hull failed at 404 pounds while trying to get to the 500 pounds and let it hold for 30 seconds. It never even made it to the ABYC minimum, let alone held it for 30 seconds..