Hi John. I've been fortunate enough never to have had a serious shoulder injury despite 15 years of top level rugby. My upper back, however, is pretty tight and taking a while to loosen up.
That said, I'm already getting fairly proficient at the 'squat' variations. I have found them much easier to perform at near limit poundages than at lighter 'drill' weights (say 75%). I think it's probably because I'm having to explode with the heavier weights, rather than tempering the pull with the lighter weights.
Whatever, I'm making nice progress. I snatched 90kgs tonight and cleaned 120kg. Snatching bodyweight can't be far off now.
If only I could get my pull ups to progress so well!!!!