To the best of my knowledge no early war 19th Alabama jacket survived and no photos have ever surfaced showing the back. Don Toriani may have some insight but this is my best suggestion. The jackets as seen in the pics are very, very simple and are similar in cut to other militia jackets. No collar decoration, no cuff buttons and no trim detail. Therefore I surmise that the tails must also be very plain. Here's my suggested design:
Style I has two inner panels with the one overlapping the vent opening. Style II is just a simple vented back. Two brass buttons would seem about right for this jacket.
Lacking a surviving example or pic, I believe a Style II is a reasonable assumption
Rick