Third jump lesson; Duke getting back into it

For today's jump lesson, John gave us a little height and a little challenge.
We started with ground poles and a vertical; then a second vertical.
Rather than add the third oxer, John had us ride through, halt, do a turn on the forehand (which was absolutely pitiful), then ride back through the other direction.
Then we went back through and did it just one direction, with flow, until Duke did one absolutely perfectly.
As always, he gradually made the fences higher (ending at 3'11" -ish).
The biggest instruction to me was not to let him rush, and to slow him by using my upper body to sit back (and to open my chest), and to remember to use my damn voice.  After a couple times through where I thought slow and said 'whoa-whoa', Duke got the hang of it and rounded himself up and over instead of plowing through.
John had us work a bit to start on the flat, as well, trying to get Mr Strung Out round and do some half decent transitions.  We did some haunches in, outside bend, and - I think - inside leg to outside hand.
I thought the halt, turn around, and ride back through was terrifying, because it didn't look like we had enough "runway" to get through the fences, but Duke had no problem with it.
He was also much better about not rushing on the far side; I could easily halt him, or trot, or do a nice canter around the corner, unlike the first couple lessons where we were basically ramming the wall.
One time I let him drift left and John told me if I did it again, I had to ride without stirrups - I had to look up (it's easy to look down the line at the letter) and keep him in the center.
We talked about Duke's attitude, possible causes, possible solutions, and his diet.  John said he's put on enough weight now, it was just how much he was losing each trailer ride last summer, and he was too skinny by the end, so it is better to start him a little fat this year.  He said if he starts losing weight, we'll increase grain again (I replaced half a scoop of senior with half a scoop of rolled oats and cut out his evening beet pulp).
It was a really satisfying lesson, although the flat was not beautiful, the jumping felt a lot better than the last couple.  It was definitely too much time off.