Whitebear, are you building a particular style? With a 36" barrel, I would be inclined to use 2 loops, but the style of gun you're building would influence the choice. With one loop on a 12 inch forearm, placed in the visual center (centered between the mass of the lock & panel, and the forend cap), that leaves a lot of unsupported forend. If placed forward of visual center, it would look odd. Using two solves this problem.