One question - Won't bubbles fill up that space under the diagonal baffle? You might collect a lot of scum under there as it fills up with air. I'm not sure it will have any impact on the effectiveness of skimmer.
Do you have a way to adjust the height of the collection cup? You can probably get a big rubber band or o-ring that fits snugly around the cup.
The bubbles dont seem to make it far enough down to get below that baffle.....so I'm not gonna worry about it, and the collection cup fits pretty snug, so I can move it up and down and it stays put. I'm gonna put a rubber band in there at some point.