Yes you can.
I was just at a SW meeting through another board. And one of the guest speakers did a study on Acropora and showed us the results. When he fragged some pieces and mounted them, he mounted 1 upright, 1 sideways and 1 upside down.
The one that showed the quickest growth was the one mounted sideways. Imagine that.
But he said the reason why he tried it like that was beacuse when pieces break off in nature, from his diving experience, they normally lay on their side when broken off and start growning like that. So he did the study and it showed that frags mounted on their side had the best and quickest growth.