Nice work for a beginner! Very nice!
There is a tool available from the leather-working tool companies that lets you mark where the stitches are going to go--each hole--and then a punch of some sort that makes the holes so they go straight through.
Also, I'menvious of the 3" bbl Ruger SP101. Is it a .327 Mag? I see the rear sight, something lacking on the .38 and .357 Mag.
So, where did you get the leather?