the biggest issue with low impedance loads is heat. If the amp doesn't go into protection, you can help the issue by massive cooling. I ran a HiFonics Thor at 2 ohm stereo and melted the plastic power input plugs. I hard wired 8ga to the board and cooled it with three fans and never had another problem.
Basically, if it doesn't go into overcurrent protection, then keep a ton of air moving across it and you may be ok. Course, the correct method is to get an amp that is rated for the load.
.5 ohm loads are only a good idea if you already have the amp. Just split the load to a pair of amps at 1 ohm since that is more available. Or get an Orion HCCA.