Hi Charlie, yes the STL export will have the same issue initially because it is also generating polygons, but you can solve it by adjusting some of the options.

The 2 main things to modify is drag the slider towards the "More polygons" side, and put in a distance value in the "Divide larger than" option which will divide any polygons larger than that.

For the "Divide larger than" start with value around 1/10 of the overall width of your object like in your case here try "Divide larger than" = 10.

That will make a result like this where there is enough refinement to get that slightly curved area to come through:



- Michael