I refined the truck design a little over the holidays, and assembled a couple of test prints. The mechanical aspects are fairly good now, and as you can see it equalizes quite nicely. I just have to improve the supports a little so I don’t lose any more brake beams!
Pembroke:87 
Assuming no one forgets to tie down a train and cars never run into the turntable pit, I suspect there is no where on your railroad that will even approach the rigour of that test.
How many of the coal cars are there going to be?
You’re right about smoothness, especially after all the tuning required by 1120. I’m planning three coal cars, but might go for four so they run in pairs.