My diving kong isn't very far at all, maybe 4 feet tops. But one day I just wanted to try a double! So I ran at my lengthwise picnic table and tried it. Just pushed as hard as I could off the front of it while jumping, dove (while spotting where I wanted my hands to land), and planted. I didn't clear the table, but it was easy enough to bring my feet under me and land on my feet/knees. Doesn't hurt at all to fail and even if you clip the end (which I have) you just land on your hands onto the ground. Doesn't hurt so long as it's soft. As far as progression, I'd say just try it in as small gaps between both of your hand planting spots and just try to increase it each time. Other than that, you just gotta go for it!