I’ve got no photos, but my current ‘bar centre’ arrangement can be seen on this video. I like them; maybe a little narrow for maximum control at slow speeds, but I still use them on steep climbs. Most use on road and canal towpath sections, though, obviously. As others have said, they make a comfortable additional hand position. Aerodynamic effects are there, but very secondary.
I also use bar ends on all my bikes (the bike in the vid has had them added since) and still use them a lot. Bar widths are ~700-720mm. From a practical PoV, I’ve found that for me the big thing is that wider hands cause the natural angle of the palm to turn in more, if that makes any sense? So having a good inward bend on the bar ends becomes more important – this is made more extreme by the tendency for wide bars to have more back sweep, of course.