I defiantly like the handle down low because when Trucker gets scared if I keep him really close he is able to keep moving.+1 to Pinkspore here!
I think you'll find that the elasticized wait leashes actually allow you greater control of a pulling dog. I've used mine with my parent's 55 lb retriever when she started running after a squirrel and it was SO much better then the arm-jerking feel of a regular leash. The bad back part might be tricky though...depends on where in your back the problem lies.
I also have the Ruffwear Roamer and I swear by it. My current dog is very much a loose leash walker and is great off-leash, so I primarily use it for running nearby traffic. It has a handle down by the clip so that if I need to keep my girl in close to me I easily can. Highly recommend it!