What is "the SitD grid"? I have never heard of that!
That is my own term. As an example, on the quilt I am currently making, I will stitch in the ditch edging my 12" blocks. This stabilizes the quilt a lot. I will then go back and FMQ outline the features in each block.
Through many errors, I have found that it is very important to press the top and backing very well before I pin baste. I hate ironing, but there is no way around it. I use spray sizing to help the process. Having the surfaces well pressed and the pin basting really secure helps with all sorts of quilting. I especially noticed that my SitD went from ugly to nearly invisible. While I had a good teacher whom I miss greatly, I am hard headed and had to find some things out by experimentation.