[WheelsAtLarge]

The vehicle needs to be moved around above the water. There's a limit to how much weight can be moved around on the transferring boats. So that's why weight matters.

As far as why fiber is a better choice, the bigger the sub the more people it can carry. the more people it caries the better the company can cover costs. Specially since the sub cost is a one time fixed cost and the supporting costs are recurring variable costs. So it's worth making the vehicle as large as possible. Long term a bigger sub will be a better choice to get to profitability.

It's all a guess on my part.