A History of the Crusades, Vol. III: The Kingdom of Acre and the Later Crusades by Mr Steven Runciman has the following statement in it:
On the breast of their tunics the crusaders wore a cross of blood-red cloth. Those who returned from the crusade wore the cross on their backs.
I haven't found this anywhere else.....yet. It's interesting to note that with all the privilidges accorded to someone that went on crusade to the Holy Land (safe keeping of his possessions, no legal proceedings against one's person until their return, etc) that they would place a very visual symbol of their recent efforts on the hardest spot for one to be easily recognized upon their return from theater. When traveling home, most likely by foot (even after sailing home to a nearby port, as they would have already surrendered any personal wealth they had carried), one would see the returning pilgrims front and not the rear of his coat.
With the additional of an air of mystique about them, due to their distant travels, I would think it would have served them better on their front, to ward off miscreants, or open the donating hearts of those who couldn't make the pilgrimage/crusade.
They too probably had their share of "stolen valor" episodes with some donning the Cross, who'd never made the trip, but sought to gain the fame and privilidges of returning Crusaders.
Again in resources covering the Reconquista, the crosses were placed upon the right shoulder. It should be noted that the privilidges and remissions given by Urban II in 1095, had already been done so by him to Crusaders fighting Moors on the Iberian peninsula years earlier. By 1095 the Papal authorities seemed to have perfected their approach to "recruiting".