Couplers before trees

I thought I'd have a look at the coupler situation on the N-scale cars before starting on trees and bushes. It seems there are a two problems: it looks like there are 3 different brands of knuckle couplers in use, and they're installed at different heights. The loco coupler height seems much higher than that on just about all the cars, coaches and freight cars combined. For this video I cherry-picked the car arrangement so couplers between neighbouring cars were at about the right height. Random trains of cars just won't work. I need to figure out how I'm going to fix up all these rather tiny coupler units. In the meantime, here's an N-scale train zooming across the trestle - at least the track isn't causing decouplings.