That's a common issue with Cura, and one of the reasons I went with Simplify3D. (Especially when I started looking at the 3DLabPrint planes.)
Not saying you need to buy a $100 software package to print a "Free" plane*, if you scour the internet there were some work arounds with specific Cura versions. But after an upgrade where Cura wiped out my entire setup library that was the last straw.
Happy to say I haven't looked back. I can honestly say I saw a marked improvement in my prints after switching.
Attached is a screenshot of the Lwing section 2 in Simplify (I'm working on the build files now and will start printing this weekend.)
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*We all ought to show LocalFiend some love for what he's given the community!