I'm doing my own experiment also so will keep a look out for your results.  I'm about to go back to un tracked as my sales have gone down since I have been uploading tracking not only that but I have had to put the cost up for each item by $1.00.....I am footing the other $1.00  So out of 200 sales this month that I usually send as a letter in am out of pocket $200 as usually they cost me $1.00 to send.

Hate that my buyers have to pay more now and I lose money too.

Damned if you do and damned if you don't