The Starboard Ace 25' is a great board for flatwater, touring and small downwinders. It has a volume of 308 Liters and the Carbon weighs 13.48 KG. I have the AST version and find it to be very stable, and this is thanks to the instep deck, which lowers your center of gravity. It's the fastest board in the Starboard range, just beating the Ace Pro 25".
Its a great touring board because the instep deck provides a sort of bowl for your tents, clothes or food. It is a useful feature for touring because your touring items will stay in the SUP.
It is also very good in small downwinders, but if you are looking for a primarily downwind board, then the Ace 27" or Coast Runner may be a better choice (depending on your weight and stability).
The best place to stand on the Ace for me is over or behind the drainholes for downwinding, and just in front of the drain holes for flatwater. The Ace is perfect for races like the Creek to Creek and The Qld Titles where it was featured with 5 of the top 10 riders.
Flatwater and small chop is the Ace's speciality. There is a slight concave on the bottom for added speed. The Ace has a spoon nose which is great for catching chop and it seems to make this board more stable. The spoon nose does not seem to slow down the board. To conclude the Ace is a great board for small downwinders, flatwater and touring.
Trev