I have an IG Vinyl and one strict rule is no jumping from anywhere but the board. Two reasons...some kids bring in toys that could sink, be hard, and if a foot lands on one they can break a foot or cut the liner. Second, at the deep end the walls slope toward the middle and if one jumps off the edge the feet can hit the wall and the head can hit the coping or the wall. I've had people argue that kids jump off the sides at the town pool all the time. I don't run the town pool and the town doesn't run mine. My pool, my rules, not open to debate. Follow them or leave.
Al