The SparrowHawk straddles the border between aircraft
and ultralights ...


How does it straddle this border if it is an ultralight?
There are so-called 'fat ultralights' that are overweight,
are carrying more fuel than permitted, have a higher
stall speed than permitted, and have a faster 'cruise
speed' than permitted. Any of these makes this unit
technically an aircraft and itis thus illegal. Some
of these same aiarcraft are registered and have an
N-number.

I am aware of a case in which a kit-builder tried to
fly the same aircraft both as registered aircraft and
unregistered ultralight by simply removing the N-number
on occasion. I'm guessing this was found to be fradulent
when the machine was involved in a fatality.

Now, if that machine was forbidden to cross the border,
how can the Sparrowhawk straddle it. It's citizenship
must be declared for one camp or the other on a unit
by unit basis. This is not new; look at the Kolb ultralight
kits. They are flown both ways, as are other powered
ultralights.