Volume is not a standard consideration for wakesurf boards since you're being pulled by the boat, not paddling. Surface area (length x width) is more important to maintaining trim in the wake...Thickness is a personal preference (skim style is super thin, surf style is thicker, and everything in between). The shape of the rail on thicker boards will determine how reactive the boards is as a thinner rail will dig deeper into the wake and a thicker, more volume rail will "slide" up and down the wake face.