You have to trust your senses when working. These cuts were made with my eyes closed, no marks to follow. They are all mostly square and plumb, within 1/64. We are all born with this capability. I'm definitely not trying to brag here just trying to help. I was standing straight up because I can't bend at all well.
Jim
Lowell try it for yourself I would think you would be happy with the results. Most of the good sawyers I have seen start their cut carefully and once the saw is engaged they cut away. I believe they pay more attention to where they are going to stop then any marked cut lines. This would not be so true for long rip cuts but for joinery work I think it holds true. Just watching the videos in this thread appears to back this up.
Jim