What a great target they'l make, Fifty of those things in the air with no protection for the riders.
Angry boy scouts with spud guns will bring them down.
300lb, that would be one soldier with combat gear, some water and ammunition for personal use.
I think they need to be able to take a payload of at least 600lb to be useful as any type of supply vehicle.
Completely visible to radar at anything above about 50ft.
