The Osburn 2300 Wood burning Stove measures 31" tall with legs and 31 5/8" with the pedestal base. The outer width of the unit is 24 1/2" with legs and 24 1/4" with the pedestal base. You can see it here:
Osburn 2300 Wood burning Stove
While it is generally recommended to have at least 12" of vertical piping before the first elbow, Osburn does not specifically make mention of this being a necessity. Please keep in mind however, that the more vertical run you have before the elbow, the better. Stoves have a better chance of establishing good draft initially if there is vertical piping in place on the flue collar.