My old SR4 / 25 Hp- manual trim was adjusted depending what I was doing:
Cruising it was out on the second outer pin (outer if was guaranteed flat water & not many stops) or second from fully down if on rescue boat duties.
Only just got the PT retro fit onto the Merc, and not had a good chance to "play" with it 'coz the first 2 trips were running in, but initial experiments are hinting that I'm glad I did it - you can hear the engine note change at constant throttle setting by trimming up when on the plane. Handling in lump is also vastly improved when it's in the right place.
As for lifting, looks like I'm going to get lazy.....