Is the fluting the same for all cars? And is it decent when compared to a manufactures car, or even a 3d print? I'm curious about those who have used these sides.
He makes fluting for PS, Budd and ACF cars that are slightly different from one another, as were the prototypes. The PS and Budd are shown here:
https://unionstationproducts.com/fluting/I was able to get some ACF fluting years ago by emailing a request.
Here is a photo of a USP side (which I labeled in my gallery as a coach, but is actually a 14-4 sleeper). This will give you an idea of the overall effect. I am pleased with the outcome, but... it is not in the same league as, say, a Kato car out of the box. Patience and care go a long way when working on USP sides, as with most model building. Note that I don't have the letterboard installed yet on the model in the photo. The kits include narrow strips of fluting that are installed fluting side in that mate with the fluting to form letter and number boards.

Here is what a side kit looks like-

Hope that answers some of your question.