flushing question with amanda-2.6.1p1

Hi list,

After using Amanda 2.5.1p2 for a while, i'm configuring the 2.6.1p1 and have a couple of questions about the meaning of taperflush and more generally with the tape utilization improvement ( for LTO-4):

I read both amanda.conf's man and http://wiki.zmanda.com/index.php/FAQ:Why_does_Amanda_not_append_to_a_tape%3F but always don't understand what taperflush is used for and what's the difference between taperflush and autoflush.
Can someone simply explain the difference ? I currently use autoflush to flush dumps which failed on previous run.

An other question: i want to dump to holdindisk before writing to tape. I found the "flush-threshold-dumped" but i want to dump incremental once a day from monday to thursday (and a full on friday) and flushing to tape at each run, so i can't wait for a dump threshold to be reached before writing to tape.
To be almost sure of flushing dumps to tape at each run, can i use "flush-threshold-scheduled" without "flush-threshold-dumped" to do this job or is it only defined with taperflush, autoflush or other ?
In an other hand, what can i do in order to improve tape utilization with about 10-15Go by incremental run and with about 500go by full run.

Thanks in advance for any hints

Thomas