Fly's as they are used in modern re-enactments are generally incorrect to begin w/. I can recall only ever having seen one CDV w/ a fly used as a front porch as is so common in re-enactments.
There is FAR too much tentage, of the wrong type, at most events. The
CS army in the field was usually issued tent flys in place of the standard A & wall tents as it was easier to produce, took less material & easier to transport. And they were typically put up as wedge or an A tent w/out the ends.
There are far too few sibley tents in Union camps, especially western theatre events. The Sibley was well liked by the men and common through late 63. I see far too many big Wall tents in Union &
CS camps.
I have seen CDV's of all sorts of tentage; from french bell tents, Sibley, dogs, lean to's, A's and even a few walls... but only ever one fly; IIRC the context was a Sutler tent.
THat said... check w/ your unit and see what they allow. Family friendly usualy throws a lot out the window. It is a sacrifice I am willing to make. My wife, daughter & other two female civilians have the wife's Baker tent, I sleep in a dog tent.