Overall height: 32"
Vital Statistics: 10", 23", 10"
The widest point is 7" down from the top. All measurements include foam edge, so you'll have to cut your "core" material 5/8" short in all directions (or however thick you plan to have your foam).
Calculations:
a = .5 * h * (b1 + b2)
a1 = .5 * 7 * (10 + 23) = 3.5 * 33 = 115.5 sq.in.
a2 = .5 * (32-7) * (10 + 23) = .5 * 25 * 33 = 412.5 sq.in.
a1 + a2 = 115.5 + 412.5 = 528 sq.in.
-Luke