The Serenity 5 is now called the "Special Edition". Our Marvelous Moderator has the right picture for it. This spa can run no problem on a 40 amp GFI #8 wire. The only reason to upgrade it to a 50 with #6 wire is if you might want to upgrade your spa years down the road and not worry about replacing the GFI and all the wire.
Nice win by the way for your friend. As HTM mentioned, they download the operating guide right from Hydropools website. If they want it in hard copy, call 1-800-465-2933 and we can send you one out.
Let me know if I can help in any way.
Steve
P.S. Thanks Lori but you gotta stop putting that kinda pressure on me in your title!