I am trying the suggested 1 mb piece size in Tixati 2.66.  I usually use 512mb for this reason:
my bandwidth is really low to upload to users.

What is the recommendation on this?  How does the auto piece selection work?

I recall one index I was having problems with getting ups completed and such mentioned
the piece size to big.

Currently I have some seedbox help on this.  Does that make much difference to my shares
locally at the PC in Tixati?

I think the auto piece size selection on new seeds is trying to not allow the # of pieces to grow too large, but keep the piece size as small as possible also.  There's an optimal balance.  But I don't think it matters too much if you're a notch or two to either side of what it auto-selects for the piece size.