I like your design, I have one of the dine-a-chook feeders which I got to try it, but I feel it's a bit over engineered and I'm not that fussed with it. the smaller pvc tube inside goes down to low, and the bottom is a bit deep. I have to bring it in each night or the possum will stick his head in for a feed, as I use mine as for when the girls are free ranging, so I like that yours is lockable.