With all of your advice in mind I went out today and took the centre divider out of my float, then I loaded Darcy in. When I first shut the ramp he turned around backwards to look at me, so I had to turn him back around again!
Then I asked him just to move forward, backward and sideways in his double bay for a few minutes. He once again had no problem moving his forequarter but his hind was a bit stuck, although he did give me a few good tries of moving his hind from one side of the float to the other. He didn't however offer to disengage his hind (definitely an emotional thing), but I didn't pursue it as he was at least moving around a little - even if it was only a shuffle. I will try again tomorrow and see if he can offer me his hind.
Then my Dad took us for a drive around the estate and I went with Darcy in the float to observe what he was doing as well as to be there just incase he were to go down in the larger space. I did film a little bit too, which I can upload later if anyone is interested.
Here are some observations I made:
Darcy will choose to stand on the passenger side of the float so that he is able to do his brace where he pushes to the left. He would only move into the centre of the bay after I asked him to move sideways a few times.
Darcy was unable to scramble, but he did however spread his legs a lot a couple of times, especially when he was bracing. His hind took over about 1 1/2 bays a couple of times.
I would like to float him like this a few more times to see if he gains confidence with the larger area, as well as getting him more comfortable to move around inside the float. Then the plan will be to float him with Khmari and without the divider, so that if Darcy tries to brace he will push on Khmari and hopefully Khmari will have a go at him and it might discourage Darcy from bracing so much.