I detailed both the UP Executive and Challenger Observations and did NOT make any modifications to the car because it was unnecessary. Yes the posts are visible if you look for them, but with people in the car, viewers will be drawn to the people inside and not the vertical post. I also did not alter my two Pennsylvania Observation cars when I painted seats and added Presier 65602 Seated People that I painted. The 21" Pennsylvania Observation cars are similar.
Draw attention away from the posts by the placement of the people in your car. The rear car body rests on the chassis plate when assembled. It is screwed in the front and the rear assembly is adequate to hold the car together. Once it is on the track, there are no issues. Adding a drumhead is nice, but will this always be your last car on the train?
There are times when Lionel's designs need owner modifications. I do not believe this is one of those times.
Sincerely, John Rowlen