Cutting Two Vaults

Hi,

I'm having trouble finding a way to create a dome-like structure made of 5 (or any other number of) vaults, which have a common center.

Here's an 1.png - a pentagon, two vaults extruded (from center of and to the sides of the polygon).

The Issue

I want to remove the portion of the the two vaults as shown in 2.png (marked with blue contours).

I've tried 3.png, but from the image you can see that it doesn't work (or at least i can't get it to work). 

I've tried extracting a curve from the intersection of the two vaults and use that new curve, mirror it and create a surface with EdgeSurface (EdgeSrf) tool, but from 5.png you can see that there's a little bump appearing on the ridge of the vault (marked in blue contour). And my goal is to have a straight, horizontal ridge (marked in orange, continuous line in 5.png) 

How do i get a straight, horizontal ridge on a vault like in my case?

I've uploaded the GH file -"Pentagon Vault"- in which i'm trying to solve the issue.

Any Ideas are appreciated!

Thanks