Posted for "Berni" <bbreen@cableone.net>:

 I am not at all sure my problem was the same as yours but it was similar
 enough that I thought I would respond.  Following a condition inspection
 performed by an A&P my buddy and I were transporting his Lancair IV back
 home.  We took off and upon leveling off, heard a strange flapping sound
 that definitely got our attention.  We slowed the airplane down immediately
 and told departure we wanted to return to the field ASAP.  Once the airplane
 slowed, the sound disappeared.
 
 
 When we got back to the hanger we started looking for something
 loose.couldn't find anything.  We jacked up the plane and swung the
 gear.still nothing.  As a stab in the dark we decided to reposition the
 springs on the gear doors to create more pull upward when the gear was
 retracted.  Other than that, we changed nothing.
 
 We took off and never heard the sound again.
 
 Berni Breen