Just outta curiosity, what kind of span are you working with? Point to point, like a suspension bridge, or is it just over rough terrain?
If you just need a flat surface to make it over rough terrain, I'd suggest something like the first design below. Red is lasagne, blue is pene, and green is linguini. Nice thick lines, so it's wider than linguini or fettucini. In between the two flat portions, you could layer two or three sliced pieces together and have a nice strong support
If you need a suspension bridge, it's still mostly the same. Nice thick boxes of lasagna, reenforced with linguini as your columns. Layer several pieces of linguini together and have them form your top wire, and then some small spaghetti columns as your support wires.
Maybe. I could just be talking through my hat here...
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