Arched top door issue

[jkershaw]

As part of an adaptive reuse to an existing 1920's warehouse, we are infilling an existing arched masonry opening with a new door. The frame will be a 1/4" steel plate, and the door will be arched (no transom).

The "D1 Segmented 20" object would seem to be the perfect object to use in this instance, and as you can see from the images, it's 90% perfect. However, the top of the door is not conforming to the shape of the frame.

I believe this is due to a missing parameter in the object - the "upper tolerance" parameter. This parameter is customizable with other doors (see image of "D1 20" object, for example), but is not available on the D1 Segmented object in question.

Is there a solution to this issue?? Unfortunately, 90% perfect means 100% unusable. Please help!

Thanks!