Also, yeah. To agree with above post you need to consider every aspect of design for every tire. Tires are all engineered for very different purposes. above all, you want a tire engineered for longevity AND carrying capacity. You might find a tire with super hard, thick tread and 120 psi max psi, but if it wasn't made to carry weight you'll just blow out the sidewall... Sounds like moped tires all the way if you can fit them. I didn't read every comment though so maybe I'm just spouting at this point, but... yeah. moped tires are designed for weight. Bicycle tires, not.

Also, do you have any pictures? We're all curious. hahh