I am having this same issue. Did you ever get the caps off?For the love of Pete! I can't get the plastic covers off. Well, I actually got one off but it came at the price of damaging it. I had the GX in for the 10,000 mile service today and asked them to show me how it is done. They were also not able to get them off...even with a trim tool. They wanted me to set up a new appointment so that if they break them, they would get replaced at no charge. I have two requests.
1. Please post a picture of the trim tool that came with your GX. I have the torque wrench and plastic covers but did not see the trim tool.
2. Post a video of yourself using the tool to take the cover off.
I know these are big asks, so for your trouble, I'll buy you a beer next time you are in Minneapolis. And you can also know that my family will think of you each time we hit the freeway with out the extra wind noise that the cross bars generate.