Group structures and tricks

Taking Villa example, just to know the structure and effective rates for qualifying 75%. Villa is parent A is sub 100% - F is sub-sub 80% V is sub 90% - C is sub-sub 80% Now if F makes loss of $100K. I can surrender it to A ( as it holds 80% of control ). But If I surrender it to say "V", will it be like this prcedure? ( 90% x 100% x 80% ) = 72% disqualified * ? Or if I surrender it to say "C", will it be like this procedure? ( 80% x 100% x 90% x 80% ) = 57.6% disqualified?? I am aware that how to deal with the desending like from main parent to its direct and indirect subs, But I am confused when it comes the time to check cross pairs of subs with other subs or sub-sub with other holding C. I saw your lecture ( wonderful ) on Villa example on group loss relief. I was confused on recalling it, when I saw you have chosen the V company as claimant after A claimant. So I was deriving at effective rate that was 72%( as above * ). Let me know the easiest wording answer, so it will be easy for me to understand precisely, without having to guess for your answer scripture :) Many Thanks