I think you should make it like an acoustic guitar, bending the sides and all, If you have a 60mm body, then carve all that, you`re wasting a huge amount of wood, and also the thin sides and back of a real acoustic are there for a reason.
one more thing, 4mm for the top seems too much for me, i`d go for 1,5/ 2mm with an X bracing, you can go thinner if you use a lattice. this will improve the sound of the guitar.
I`m building one based on the dreadnautilus guitar but with a bracing not as complex as carlson`s original... with a bolt on design that lets me remove the neck to travel.
let`s see how that turns out.