I used a bar clamp, and a cord to a bucket full of water to hold the chine at the correct angle. A towel soaked with a few kettles of boiling water gave the oak enough flexibility to twist.
A Japanese pull saw really is the best thing since sliced wood.
I was pretty happy with the result.
The chine on the other side is another days work.
Realising that It would be easier to do the slot for the Center board case now rather than later, I took a break from steaming. I used the template that I made up earlier and a cheap and cheerful JCB 1/2" router. I just used a simple trim bit without a bearing (the shaft acts as a bearing). I cut out most of the centre of the slot first with a jigsaw. This made for less routing and less sawdust), but it did mean that some of the cut was lifting the grain. Not usually a good plan . Luckily Epoxy, and the fact that this will be well out of sight will save the day.