Quick question: Before I cut off the shaded area on the trim control horns that include an extra hole, I'm curious why they come this way? Is there a reason you would want to keep the other hole, maybe for different type of trim setups?...
If I understand what part you are talking about, I believe they come that way because you trim one side if you are installing the manual trim system and you trim the other side if you are installing the electric trim option.
I just realized you posted in the RV-10 section. I was thinking of the 7, so I could be off base...