For what it's worth: when I first tried split grade, I did it like you, grade 0 first followed by grade 5. Didn't have much success. But then I went back and did it the other way around. Now don't flame me, but for me I found it a lot easier to get the contrast right that way. I do a test strip and aim for the time that gives me just black on the very darkest part of the image. Then I add in enough 00 for exposure. I flash high contrast negs with the neg still in the enlarger, no filter and a piece of white translucent plastic as a diffuser. I'm sure loads would say that's all wrong, but I find it easier than straight printing.