Yeah, this is not enough info.
On the tops of instruments in the violin family, the mandolin family and on archtop guitars, there is, for lack of a better word, a recurve all around the edges.
To see that accurately, you need contours perpendicular to the Z axis.
I’m struggling for the right words here, but I think the recurve, a short distance where the plate is slightly convex, moves perpendicular to the outside edge of the instrument.
Iike, you could model it roughly by offsetting the outside edge by 1/2" and 1" inwards, gumballing the middle curve down 1/8" or so, and lofting.
I’d do the whole thing in Clayoo if it was me, but it’d be a multi step process and it’s not a cheap plug in.