Hello and welcome. I am new to this site and am also born and raised in the Bay Area (Alameda and Dublin) but have lived in Kentucky since 2005. There seams (pun intended) to be some very helpful folks here. I hope you can figure out the diagonal seam thing. I am not sure exactly what you're doing but I have seen people use a tape in their machine that has 3 stripes on it and they follow the middle line to help keep diagonal seams straighter. I'm not 100% sure that's what you're looking for but thought I'd throw it out there for you.