7 years ago I laid out a Great Auk from offsets in CAD program VectorWorks.
It wasn't too hard, a lot of busy work. I made target points and then moved them to the correct position by entering the coordinate points from the offset charts. A bit of a fidget VWorks then only would coordinate the upper left corner, it'll now do centers. I just shifted everything(including centerline and waterline) by 1/2" or 1".

After I established the points, I used vectors and pulled on the handles to fit curves to the points.
You'll also be sanding the forms to meet the lines, so unless you have flat spots, the curves aren't that critical.

If I did this again I would use Adobe Illustrator simply because the current version of VectorWorks (that I happen to have as an academic version) is still clunky and slow and I'm used to Illustrator. A CAD app has 3D features that could be useful.

I've never known Excel to keep the same scale graph to graph. I'm probably missing something, if you're not sure, make sure this won't be a problem.
Also, is it necessary to use both sets of lines? buttocks and waterline?