Not to hamper your numbers, but they are off by 2x. The lightest double/twin rope is ~33g/m, so 30 feet would be 300g (2/3 of a pound). The lightest single rope is ~48g/m, so 440g (~1 pound). And solely for hauling Lottie, a 5mm dyneema static (15g/m) would be entirely sufficient (1200kg strength), though harder to get a grip on. I’ll get my coat.