That's very helpful thank you very much William. I didn't realise that they are flat sections. What do they fix into at each end? Presumably it's a channel, but does it have cutaways or ports to accept the bows? Do you think that a round section replacement would be able to 'lock into' the side channels?
I'm a bit worried that if I use carbon or fibreglass it may pull the sides into a funny shape.
AS you say, I was hoping that removing the side trims and the window surrounds would enable me to access them without taking out the screens.