I made a flat braid split pouch sling, out of 3 gutted paracord strands, folded in halve to make 6, with the split pouch long like above and flat and equally wide as the sling straps, like my previous designs, but now simply with a longer split, like above.
I gutted the paracord to reduce weight and stiffness of the end result. Leaving the innards in makes it too bulky. 

The versatility of it is amazing, the sling now has the ability to sling any rock 50-500g reliably. No need to swap slings.