Sumo definately does feel easier but still not 'right'. Squats are better for me than the deadlift but still difficult because of my lower body hell.
How tight are your hamstrings and hip flexors? Do you still find you walk around with an excessive lower arch or are you programmed to stick your body into a more neutral alignment all the time?
My hammies aren't to bad, but my hip flexors are. It's annoying really.
When i walk I still have lower arch, but not as bad as it use to be. It's actually my old doctor that suggested I do weights, not only to help with my back but also because I was a bit under weight.