Hey, Conaill -
I was thinking about the curved wall, too, but I hadn't thought about the issue of wall thickness. If you're using the 45 degree walls solely to join up with straight walls on both sides, I may have a solution.
The top pic shows what the easier version would look like, and the bottom pic shows the solution:
You would make a "notch" of sorts for the straight wall to fit into. Make it overlap the straight wall by 1/4", and you've got the right thickness.
The only thing this method won't do is longer diagonals, and it won't look right ending out in the open that way. It's only good for joining the size shown, but it's a start!
