If the oil drain plug is 19mm, maybe an 11/16 good quality six sided socket with the bevel milled or filed off would work.
When I made the post above, I was not where I could check my TW. Since then, I have determined that an 11/16 will not fit. Furthermore, no milling of the beveled edge of a socket should be necessary. There is plenty of depth to the drain plug nut, unlike the F650 plug that was underneath the crankcase and only about an eighth of an inch thick.
It is important, in my opinion, to use a six point socket and not a 12 point. Better yet, Snapon
offers six point flank drive sockets that put the pressure on the sides and not the corners of the fastener, albeit a bit pricey at $14.75.
Has anyone stripped the drain plug with the closed end wrench in the factory tool kit ?