Ive done a bunch of testing with the AP 3ks, and Im not sure how you got them to do anything at .5 bridged. When I had mine, it would go into protect automatically around 1/4 volume (still holding just over 14v), when bridged at a 1ohm load.
When bridged at 1.4, it still didnt like certain notes (Im guessing since my box had almost 0 impedance rise), but would play music just fine 99% of the time. Killer amps, though. Got mine new for $285, and was burping a 150.1 @ 37hz with a single amp and 2 subs with my blowthrough..