I just installed lenco trim tabs to a 2017 Chinook which doesnt use the same transom design as your boat. But is similar enough I feel I could help and provide some advice. Firstly, the screws are useless. The screws have course thread and your transom is only 1/4 inch thick. Go to Rona and buy a box of 50 1/4-20 stainless nut and bolts. From what I've gathered from your thread, you're basically ready to start drilling. Mount the tab to the trailing edge first. Then adjust the angle of the tab and the location of the cylinder mount. I would rather have to drill the trailing edge twice instead of the transom twice if I screwed up. Goodluck!