I hate to jump into this as it seems to be between just the two of you. But, that what the 'pen is for.
If you move PS to Friday night and he pitches well, you may still lose that game because we aren't hitting opposing Friday night pitchers very well. Then if SM gets lit up on Saturday then we may not be winning the series as we have been even though we seem to be scoring more runs on Saturday than Friday.
So I'm fine leaving the rotation as is.