As usual
you are misleading. You are assuming that you will start hashing with all S3s on 14.09 while the SP31 starts hashing on 20.10. That is wrong and your whole calculations are way off. SP-Tech never shipped first batch after 15th of the month.
According to the site, they ship second half of October.
http://www.spondoolies-tech.com/products/sp31-yukon-october-batch-1Is there a reason to think they'll ship before that?