Gary, Tony & Dave My steamup bay is at about 30 inches above ground level and I have a section of about 35 feet of straight track descending to ground level with a straight run out at the bottom. For both my RH Fowler and my brothers C-16, we approximately center the Johnson Bar (reverser) while descending. That's enough retarding to keep the speed under control. We tried reversing but that locks up the drivers and the loco slides. For our Bantams, I shut off the throttle on mine and that controls the speed. My brothers Bantam must be held back manually because it runs faster with throttle off than mine.
It's a bit exciting but no terror. Earl