I play head on very often and I can confirm that the time savings you talk of do exist but you should keep in mind that you need to save time anyway because for the same number of hands you use up 33% less cards than playing one hand per round.
May be you should come up with concrete figures:How many seconds does it take you to complete a round with two hands?How many seconds does it take you for one hand?
I will also try and clock the thing.In one casino they force me to play two hands anyway.So this can be done without additional costs :-).
Without concrete data any further discussion would be useless.

Francis Salmon