I did the unthinkable, utmost sinful crime in this BBS -- I plunge cut into the corner and finished the straighter part with a pull saw. It worked! May not as nice and neat as the general consent goes but it really worked.
And I did not fill -- hoping the rough dimmples help to bond the caoming( Nick's build up design). It may be wishful thinking because I have not really test the bonding to find out. Oh, I sand the area to rough it more just in case.