2belite-
I've thought about that quite a bit before. I think in cases where the jumps are both very vertical and very elastic in nature (as in hurdle hops) that mid-foot (basically the same as flat-footed) landings are the best bet. I don't think there's ever a situation where you'd want to land on the forefoot. Here's a couple reasons why:
1. It may lead to injury.
2. It may teach incorrect takeoff mechanics that could carry over to the competitive jumps.
3. With plantar-flexion, there is less pre-tension in the gastroc complex prior to ground contact. Less pre-tension means less response out of these muscles at ground contact.
4. Sometimes super elastic is not necessarily what we want. While ground contact time may be more shorter with a forefoot landing, the impulse will almost certainly be less. We want athletes to get the greatest impulse possible off of the ground. Impulse is a product of force application and the time through which that force is applied. Knowing this, we obviously have an issue we need to deal with. That is, the more powerful or fast you are, the less time you have to be able to put force into the ground because you'll break contact with the ground sooner. However to get the most out of an athlete's abilities they will need time to put force into the ground. I think that one of the big benefits of a rolling (heel-midfoot-toe) takeoff may be that it gives the athlete a longer period of time on the ground through which to exert force.
Taking those points into account, it doesn't necessarily mean that doing it like that means it has to be less elastic. In fact, I think while the response from the gastroc complex may be slower, it will reduce amortization time and probably result in a more efficient takeoff because the muscles can fire in the correct sequence.
