Intersection of TR3 D7 D9

[TheArf]

I think I know the answer already but how important is it for this intersection to line up as per the book. I have been on this all morning but I cant get them to line up. I have taken them apart three times, checked all of the cut angles with combination set protractor, and all check out correct. I have marked out the 491.5 line on BR5 & BR6 so that D7 & D8 are pitched together. For some reason I cant get D7 to be in the right place and keep the 151 mm overhang at the very back. Bet when I go back tomorrow with fresh eyes it will jump out at me Grrrrrrrrrr