This would make so much more sence with slv and gld etc in an IRA account.
In fact instead of trying to pick an absolute value, just put 50% in each and rebalance when it gets to 45% in one and 50% in the other. Or some other ratio that makes sence.
You could take the profits and buy physical that you would not trade if you are in the end of the world fringe.
I also thought of trading gld against spy. Own whichever is cheaper or own both and rebalance once in awhile. Gld is cheaper than spy at the present time.