Damo, Having your cav/rudder plate adjustable is a very good idea. It is only narrow though so will only be able to effect trim so much, but your hull may need no adjustment anyway!
I use my adjustable plates for choppy water and crossing wakes due to my boat being so flat, it slaps badly on mild chop. The way it's currently set up needs no trim at normal ski/barefoot speeds.
I have never had to lift plates above level with the hull and think that this would cause problems actually sucking the hull down. Initially my adjustable plates were 300mm wide and I was running a fair bit of angle, the current plates are the full hull width and run much less angle, I have not had to touch these for two seasons.
I think 20mm down at the tip of your cav plate would be plenty, if you go past this I would look at other solutions, which is pretty well what I had to do.
Re; GSXR 11's, I'm a bike tragic, currently kick around on an old GSF12 which has the old oil air cooled 1157 gsxr motor.
Don't know how you got the blame for being the dislexic

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