Hosea, I used to shoot paintings of an artist before for catalog and promotional purposes. What Ortega said will give you thr most accurate, and reproducible results. The one factor that you have to look into is the distance of the lights since you mentioned that you have long pieces - light fall-off may be a problem, and if that is the case, then you may need 4 strobes instead of 2.
As for management of the actual artworks, especially more fragile ones, you would have to look into each very carefully. For flat paper, I would never strecth it, but find a way to temporarily 'mount it on a very flat, rigid surface so that I can position it easily without having to worry about damaging it so easily. If you're comfortable with it, and once you have it figured out, I suggest that you invite the artist to be present during the preparation and shoot to witness yur process and also verify that you did not damage the works.
Personally, when I shot larger works, I never liked to have it flat on the ground as it meant that I needed full vertical control - not easy. Finding a way to prop it up at eye level if preferable if you have a large number of pieces to reproduce.
p.s. If you've read this far, don;t worry about colour fidelity as you can always tweak it in PS, and verify it at the proofing stages.