According to my tests, boat offset is not taking into account when calculating distance to line. So basically what I do is when setting up the “perfect start” is to ping the RCB location when the bow of my boat is at the RCB. Sames goed for the Pin-end. Ping the mark when the bow is at the Pin-End.
I have a bow-offset of 12ft/3.5 meters. Since I start 45 degrees angle to the wind, the true offset would be COS(45)*3.5=2.5 meters 
Don’t make it complicated, just ping the marks with the tip of your bow. The GPS is far to slow to really have a precise reading during the last 10 seconds of the start. I only use it between 60 seconds and 15 seconds to start when we are actually floating on the same spot.
