OK, if you want to add a level of inconvenience (and are willing to sacrifice a bit of vanity), put your bag inside a slightly larger duffel bag - preferably one that looks old, beat up, down market, unappealing. Zip tie your bag and zip tie the outer duggel bag. Try to get a duffel that fits fairly closely (possibly a pain to get on in the first place) and align it so that the zip on the outer duffel is secured to the opposite end of the bag from the zip on the inside bag.

Then cross your fingers and hope TSA doesn't want to get in your bag for some reason. If humanly possibly, put only clothing in the checked bag - don't risk books or even good or solid shoes (slim chance they'll cause suspicion on the xray).

The outer duffel, particularly if closely fitted, adds another level of inconvenience. You could even use something like what used to be called a 'sea bag', sort of a precursor to top-opening dry bags. Again, the point is just to make it too inconvenient to bother with, without making your luggage look like an armored car carrying the family jewels. A bag within a bag, particularly when it's awkward and tricky (for you as well as them, unfortunately) might add enough inconvenience to deter anyone interested in getting in as many bags as possible.