Sending the passenger back to security for SSSS is completely brain-dead. If the passenger had to hide anything, he'd do so airside on the way to security, and pick it up back on his way to the gate.

Calling TSA to the gate for someone who missed an SSSS, on the other hand, is only completely meaningless, even if you make sure that the person cannot leave the gate area to hide something and pick it up before actually boarding, because he could just have given whatever to someone else. You would have to shut down the entire terminal, search everywhere for anything that could threaten security, call back all airplaines already on the runway and do the same. Or you could just forget about enforcing the missed SSSS...

By the way: SSSS that are predictible (like when you buy a ticket last minute and/or pay in cash) are actually LOWERING security because terrorists will know about these criteria and avoid them and thereby reduce the probability that secondaries are done on them. To alleviate this problem you can randomly check every 10th person in addition to the ones already marked for SSSS. Or, the easier and more effective way, just forget about all the possible indicators for SSSS and pick randomly. Trying to make a statistics and coming up with indicators as to who is likely to become a terrorist out of a base of maybe 20-30 people who became aviation terrorists must cause anyone knowing about statistics severe headaches anyway.

Marking SSSS on the boarding pass, is also counter-productive. The terrorist will just give his stuff to one of his partners -- or go home and try again next time.

HTB.