How do I make the sloped roof of my tunnel turn semetrically?

I’m trying to build a tunnel for a game I’m helping create but I can’t seem to find a way to smoothly turn the roof of the tunnel. To make the slope for the roof I’m using subtractive cylinders placed inside of squares. I’ve tried using editing and extrusion to try and mold in together but I just can’t seem to get it to not screw up. Does anyone know of a better way?

295402-tunnel-hell.png

A better way is to make all models outside of Engine in software like Blender. This way you will have full control over shape of you tunnel and it will be much cheaper for the memory in the end. Geometry brushes provided by Unreal Engine are pretty expensive for the memory.

Thank you for the great tip