Just for the record, you said you've moved one trim hole, does your engine remains at 90 angle when on plane at speeed while cat rides parallel to water level ?
Your case is bit different, you have a mini cat, not a standard sib, cats needs slight more HP, more drag issues to overcome fast, that's why tech plate states 30 HP. Anyway 30 is for carrying max passengers, not your case. If remaining up to medium loaded a 20 HP shoud perform satisfactorily.
On posted video, the engine sounds like it's lugging, puts tremendous effort to plane that sib out. If plan staying with current engine, install tach and go alone for a full grip throttle spin on same flat water course, check achieved max wot numbers, Could maximize prop to achieve better performance, but there's an issue, (gee, there's always an issue) you don't know current number stamped on that prop from which to go, will need a less pitch prop to rev up your current wot numbers for that cat to plane faster. Begin taching that engine, need to know achieved wot numbers to start with.
That's why was suggesting getting a used healthy 15 HP engine and prop, will have lots of prop pitches to play with and take the full HP out of that engine.
Happy Boating
