Walgensen

I understand that there are 9 flags to determine avadon's strength in the ending. I wanted to check out the romance path since it's my third playthrough, but I also undertand that betraying odil will cause me to lose a point in that section. How many of the 9 flags do I need in order to get the best possible ending in terms of avadon's strength? Can I get the best result if I lose a point?