I agree with Brent. I started getting sucky at kongs and I realized it's because instead of split foot take-off I punch and I never reached for the end of the obstacle.
Think of it this way, when you do a kong vault, do you think you're going to make it far if you place your hands at the very beginning of the table? Probably not, unless it's a double kong

. But, if you reach for the end your body also naturally goes into that "dive" position if you're doing it right, and it leaves you enough space to push forward and bring your legs through without touching the table. What I did to progress to longer kongs is just doing them, and if I couldn't get my feet over I would just land on the object. Eventually you'll find the right time to put your hands down and then it'll come naturally to reach for the end.
Uhm what is "block"?
To make it simple, blocking is placing your feet in front of you in a two-foot punch while you have forward momentum. If you punch with your feet in front of you it turns that forward momentum into upward momentum, so you gain a bit more height.