That is a tail skid. Parts for both the military and civil versions are included in both kits. The two kits seem to differ only in the instructions and decals. The military version has a tail wheel, the civil version a skid.
I missed my chance on the outdoor decals. Snow has been mostly gone for two days, but it was cloudy. The sun broke out for about an hour but I wasn't ready :-( The forecast calls for eight inches in the area! That will take some time to melt. Oh, well, when spring finally gets here I'll take some outdoor pictures.