I find that it is usually not worth while to code the vertical rigid element. The elevation change is quite small. Other than making the model look pretty, for the typical one size reduction it is not worth the trouble.

Now, when process decides that it would be a fine thing to put a 20x10 reducer on a pump nozzle, I'll model that will several step downs. Thankfully, that's only happend to me once and I think there was ultimately some flogging involved when it was discovered that that 20x10 reducer couldn't be bought.