One of the necessary tricks to checkering is to set up a light to the side of your work.
The front and back edges of the pattern are formed by where the checkering lines stop.
Strive for borderless checkering and build good habits early.
Here's another important point: The final edges of your checkering pattern must always be determined by the gradually spreading lines that you space out, one at a time.
I have a modern rifle made by a major manufacturer that has mighty nice-looking checkering areas.
I must mention a tool many checkerers find handy: The checkering cradle.
You will have the toothbrush in one hand while checkering to keep the sawdust out of the lines.
There is a picture of Monty Kennedy in his book holding a large magnifying glass while checkering with one hand.
I have read where it is best to start checkering on an unfinished stock.
Also, the quality of wood available these days is such that very few pieces are hard enough to hold such delicate checkering, and the diamonds last much longer if spaced a little larger.
This will leave room for the actual point pattern to emerge as you are checkering.
Not extending the checkering this far is OK, but I think it looks much more professional even if more difficult to accomplish.