BTW, do we need by law have to have the two amber markers on the front of the TC
NO, not in my opinion. Marker lights were probably great on tiny 2 lanes years ago. Maybe eve when cars had black outs during WWII. But they are still required Yes. I thought about the same question about leaks. Every light is 3 leaks waiting to happen. 2 screw holes and 1 hole for the wire in each light. Times 5 lights across the front of your RV and presto... 15 places for water to get in. And that is just the front of RV.
My answer was to make a inspection panel on the inside that flops down, I remove a small shelf that I put in and then the small panel flops down right where lights are. Allows me access to inspect twice a year. Rest of the time just looks like book shelf.
Still waiting for rear of RV to figure out something. Shower is in back corner and just can't cut an access hole in it.