If the Mod of the Top Loop welded to the Later MK.IV Plate was utilised. (On the L4A5) there is absolutely NO Option but to use BOTH original sling hooks.
IF, you are going to fit the sling to the TOP Loop of the Modded Buttplate.
As Peter has stated, the gun does 'roll' away in the carrying position with the sling fitted to the side of the long sling loop. The Mod of the welded loop at the top of the plate. Eliminated this awkward phenominum & stopped the wood furniture getting damaged by the rear sling Hook Assembly.