Cecil Chapman wrote...

...but how do you get yourself to do that first flight?

In my case it was a matter of whether or not I felt I
was qualified and safe to do it. I got as much time as
I could scrounge in similar airplanes, I sought out airplanes
with worse handling qualities than mine and practiced emergency
procedures, and plannedplannedplanned for every contingency
I could think of, and racticed those that I could. I wouldn't
consider myself the BEST qualified pilot to make the first
flight of my airplane (an RV-4), but I felt I was qualified,
and I trusted myself as much or more than anyone else I
could think of. I've certainly seen surrogates who took it
_less_ seriously than I did. After all that, the first flight
(video buried somewhere on John Ousterhout's website) was a non-event.
Other flights since have certainly been more, uh, 'worrisome'.

I would think a thousand questions would fill one's
mind...

Self doubt is probably a normal reaction (I certainly
suffered from it), but if my workmanship were to cause a
problem that resulted in an injury I'd rather it be to
me than someone else. If you doubt your ability to
handle an emergency, by all means have someone better
qualified fly it, but if you're qualified, are you going
to feel better if someone else gets hurt while you watch?

How does one safely test an 'unknown'...

In small steps with time to review results in between
flights.

Dave 'endpoint' Hyde

RV-4 down for engine work at 27 hours
EAA tech counselor