Hi William
I don't believe you can contact the front of an element in a column (excluding the lead element) because the rules treat element B as being lined up behind element A. Let's say however that you (legally) contact the flank of B, then I would say element C (being the next element in the column behind B) would have to fall in behind B, unless the length of the side edge of element B was longer than, or equal to, the length of your front edge (e.g. Chariot, Elephant, Train). Although I probably wouldn't do this without first protecting the flank of my element.......
Andrew