Setting a rectangular step cut citrine.

[lynseysorefingers]

Ok, so I was on here last week looking for advice on cuttin a bull stick/scorper to set a citrine in a setting I had made. I had made the setting tapered, going by the instructions I saw in 'the ring book' by jinks McGrath. The only problem is the book didn't explain the full formula for the setting. As a result, I found the setting too tapered as needless to say, I'm starting it again.
I'm sure I found something on the Internet that explained the formula but I havn't been able to find it.......maybe I was dreaming!

Any enlightenment on this would be great. I'll try and get a picture and measurements if that helps!! Just check. It's not a step cut! Size is 10mm x14mm and the height is 6mm