When running without retainer I pushed more in, as many as I could fit in.
I rode like that for a week or so; but the hub kept on becoming more draggy, and I kept backing off the left cone under the mistaken impression it was too tight. Then one day the hub suddenly became mis-aligned and I thought the left balls had dropped into the hub. But on disassembly, they were still all there despite the big play. The drag problem was something else altogether, not the unretained balls. It was the ring under the plastic seal.
I wonder whether that is causing extra drag on my hub. From the earlier discussion, I was thinking of partially disassembling the hub just to do a quick cleaning and inspection.