tenhoff I agree maybe as a starter hat but most liely you will be offered a spare hat to use from a pard. Remember hats at that time were fashionable as well as personal then as a soldier used as protection from the elements. Early war impressions kepi's would work mid to late war slouch hats. no creased crowns, good luck, when I was researching my impression I looked at tons of photos then headed to the sutler and spend spend spend...
I actually own a European cavalry hat that is newer but was essentially a holdover of 1850s and 1860s era designs that had become traditional and are still used by certain units in parts of the world as dress attire. I have a period photograph of an identical hat being worn by a volunteer U.S. cavalryman. I was told by a reenactment group that it was not acceptable or period. Then I look out and see three Confederate cavalrymen in grey Stetsons, and Union officers using "reissue" style post-war holsters.
We have photos of our ancestors that fought for the Confederacy, and two went off to war in straw hats. I was looking through the regulations of one reenactment group and in bold letters were the words "ABSOLUTELY NO STRAW HATS." The same rule show up in numerous CAS and SAS groups' rules.
I've been involved with all kinds of reenactment groups and the rules are often baffling, and "period" rules are sometimes absurd.
One more anecdote: I was involved in a medieval reenactment group and my persona was late 15th century from the Nuremburg region. I replicated a complete costume based on Albrecht Durer prints and wore it to an event - where I was eviscerated for not being "in period."
The lady's points of contention were A.) I was wearing Birkenstock-style shoes, which show up in no less than seven Duhrer pieces, B.) a large flat brimless cloth hat, as seen in his drawing of Topler Pfinzig, and C.) a loose long tunic with cuffless sleeves - a garment virtually unchanged for centuries. I had my proof that they were correct, which I presented to her, and her response was that she thought I was doing an English persona and she knew none of those things were correct for THAT.