I have a D4.  I'll have to dig out the book and see what it says for finger joints.  I thought you could do box joints without doing anything special.  Now I just have to remember to remind myself to check.

I know that the upgrade kit comes with a spacer to to either 3/8 or 3/4 fingers. The F2 and F3 do somewhere around 10 sizes and seems a little less fussy.