Zack is welcome to answer for himself, but if you don't mind I'll answer now. Zack's book is about Florida troops in the Army of Northern Virginia. The "Simpson Mounted Rangers" did not serve with that army. This company eventually became part of Maury's 15th Confederate Cavalry, which served on the Gulf Coast. Art Green recently (last few years) published a book about that command titled Southern Boots and Saddles: The Fifteenth Confederate Cavalry C.S.A., First Regiment Alabama and Florida Cavalry, 1863-1865. If you check the list, Art is listed among message board authors.

http://www.amazon.com/Southern-Boots-Saddles-Fifteenth-Confederate/dp/0788438131