Jim , Of course there are set dimensions for a cross , but you have to get hold of a scale type book that shows you what they are , I have one around here someplace . I just cut out a cardboard template of the actual size , hold it down on wing or fuse with mask tape , draw with a soft pencil the outline , remove . I use the 3M "fine line "tape & go around edges , then fill in the paint , not a big deal .