dude don't feed the Bazooka right on the grizzly bars. Introduce the material as far back on the deck as possible.
Sometimes you do need a rock to weigh it down. but, you should be able to get it wedged in some rocks and not need a rock on top like that.
i live right up the road if you ever want me to meet up with you let me know I'll help you get it set up better.
We'll get you more than a speck.