How thick are the styrene sheet you are using?
Am I seeing correctly that you run styrene sheets on the inside edge attached to the upper Hull then you laminate it with another styrene sheet cut to fit and match the edge of the outer upper Hull?
And yes I see you filled the crack and spaces with? I normally use Tamiya putty for fine stuff but this looks like it needs something more. I did finally find Bondo glazing putty, that was a chore if you can believe it.
What are you going to use for Zimmerit?