Vince, I find I get back pain when I do the regular barbell row exercise. What do you think of the single arm rowing movement, holding a dumbbell in one hand and supporting the torso by placing your free hand on a bench?
I am not in favour of single arm movements. They do not work as well as double arm exercises.
Also one arm exercises take two times longer to perform. You should always select exercises that take the minimum time and energy to employ.
Try pulley work for lats, giving them as much stretch as possible.