The height of these skimmers is what determines the efficiency. It increases the dwell time of the bubbles. They're old-fashioned and rather a pain to keep up, the diffuser blocks need to be replaced monthly to keep them working. But they work fine.
You can modify the height as you wish, just that you'll decrease the efficiency. You should be able to modify the plumbing with no issues. Though you'll never get better performance, you shouldn't do much worse.
Jeff