we have hauled our 204 sized Deere loader on the farm. I know it's not a huge loader, but I can't stick my head out the window on that one either. Since you sit centered in a loader, line yourself up with the centerline of your trailer. Also, since they pivot point is in front of the operator on pretty much all new loaders, you will see if the machine is not straight.
You could also practice driving and keeping a straight line on flat ground. Chalk/paint a line on the ground and take a few practice tries. Like Wes J said, if you can drive the truck, you can drive the loader. They really are a straight forward machine.