I just saw Broadway's video showing their new UP 4-12-2 model. It looks beautiful and I hope they sell a lot of them. They also say they have it set up for three cylinder sound. The video does show the locomotive in slow enough motion that you can count 6 exhaust beats per revolution.
However, and there is always a however, the six chuffs per revolution in the part where you can count them are equally spaced as if the drivers and the center cylinder are equally "hexed" when all of the UP 4-10-2's and 4-12-2's and the SP 4-10-2's were actually quartered like their 2 cylinder cousins with the third cylinder timed at an angle in between two quartered power strokes. Check a copy of "Three Barrels of Steam" for drawings indicating the proper angle.
Old timers that operated these engines said they sounded like they were stuttering as they went down the track and the ride took a little getting used to because the power strokes were not at an even pace.
I hope I'm wrong about this, but getting the chuffs synced correctly is very important to me. I hope someone can view these models in persons and report back about this, especially if I am wrong.