You could run a single 6 strand fiber from a 6 port LIU at point A to the first 6 ports of a 12 port LIU at point B. Then run another 6 strand from the last 6 ports of the 12 port LIU at point B to its own 6 port LIU at point C. Use 1 meter patch cords at the 12 port LIU to patch the strands from one 6 strand to the other. This will give you 2 strands at both B & C leaving 2 spare strands. Definately not ideal, but it will work.