On my Super Viking I routinely ran the Aux tanks dry... I ran a timer
so I knew within a few minutes when it would happen... The engine would
begin to lose power and I would switch tanks and hit the boost pump...
Usually did not get an engine stoppage... If I was a bit slow on the
switch the engine might stop running but relight within a few seconds
of the tank change.. On my Apache I run the tank(s) dry about once a
year to clean them out (and I usually stick a mirror in them before
refilling)...
Now, running a tank dry and running out of fuel are two different
critters... I do not allow the fuel on the Apache to go below 1 hour (6
hours total capacity) for any reason...

denny