Suspected hernia??
Two things.
1) You are hitting the same problem with sumo as conventional. You are still taking up some slack in your spine when you put force through your hips. This will always be a core control issue.
2) Having hips lower dictates the use of quads rather than PC. More back than PC is due to back rounding.
Main problem: Your lumbar isn't flat in set up or pull initiation. Then you drive directly into this slack.