V 20 (degrees)?

I need to build a cradle for my V. I can't rely on it's current shape because 1/2 of the outer bulkheads are detached and the outsides of the hull are sagging a little. Would I be correct in assuming I can build to 20 degrees all along the bottom, or does the angle change from back to front? (ok aft to foward for those who want boating terms ;D)