There's now a nice strong triangular structure in the upper third of the roof's apex. The rafters have also had some smaller box section pieces added in between to stop them from wanting to twist.
Next up - last bits of welding on the roof fitting some angle iron brackets onto which I will be able to fix the wooden part of the roof structure...
(This is taking too long - need to speed up and get done - I need to be back Volvo-ing)