To add to Bindi's correct and helpful suggestion: if you're unaware, your sling is on back to front.

The closed head of the rivet faces up against the furniture, the base of the rivet is hidden against the inside of the sling, The hooks point towards the 'outside' away from the furniture. So, pretty much 180 degrees from the way you currently have it fixed.

Good work on the restoration, and as noted above, don't be fiddling with any polishing of sears. They work fine the way they are meant to. It's the operator that adjusting