Cub Driver wrote

I was at the Moosehead Lake seaplane fly-in last weekend. There were
three ultralights that flew up from Lake Winnipesaukee in New
Hampshire, about 200 miles as the erm crow flies.
They carried 15 gallons of gas.

Then, they were not "ultralights" since Part 103 limits an ultralight
"by definition" to no more than 5 gallons of fuel.

Bob Moore