According to my research and the timeline I assembled for my own Hospitaller group, and I can not remember which source I found this information in, but the dates for the various Hospitaller over garments in battle are as such:
Up to 1248: All brothers wear black cappa in battle.
1248: All brothers wear red surcoat in battle (this change was approved by Innocent IV)
1259: Brother knights wear red surcoats, while brother sergeants wear black surcoats (approved by Alexander IV)
1278: All brother knights and brother sergeants are to wear red surcoats on the battle field, while wearing black cappas in the convent
As far as the cappa goes, I do not think it is anything more than the traditional monk's robe. In this case probably made a bit larger to fit over the armor. See the pics below. (There are lots of patterns for monk's robes, some way more complicated than necessary. Mine is two long trapezoids for the front and back, with sleeves and a hood attached.)
I can not say for sure regarding the cross. I favor the position in the center of the chest because I just think it looks better.
http://i116.photobucket.com/albums/o28/ ... 000121.jpghttp://i116.photobucket.com/albums/o28/ ... 000075.jpg
Sean L.
Order of the Hospital of St. John of Jerusalem
Maryland, USA