There is considerable information on the C-Brat site regarding trim tabs. Electric vs hydraulic, auto, and even the tabless, knife edge drag types like starcraft tom put on. (Check in the search system, use a capital AND between word to narrow the scope some, " trim AND tabs AND automatic" for instance.)
As for me, I like to set my own, for how i want the boat to feel, respond, and act. JMHO.
Harvey
SleepyC :moon