What are the dimensions of a GPU riser/PC expansion slot

[RadikulRAM]

This thing: https://images.hardocp.com/images/articles/1454524108657ceGtcd2_3_28.jpg

I'm planning a tall but thin case, as I have a lot of vertical space but not much horizontal.

My priority on saving space is Length, Width, Height.

I figured if I install my GPU on a riser, I can save some width.

 

[jtd871]

https://smallformfactor.net/forum/search/902491/?q=pcie&t=resource_update&o=relevance
http://formfactors.org/devlist.asp?FFID=-1&CatID=-1

 

[RadikulRAM]

https://smallformfactor.net/forum/search/902491/?q=pcie&t=resource_update&o=relevance
http://formfactors.org/devlist.asp?FFID=-1&CatID=-1

Sorry if I'm missing something, but none of those links answer my question.

From what I gather most ATX cases have 7 expansion slots, which measures roughly 15CM in height.

 

[jtd871]

http://read.pudn.com/downloads166/ebook/758109/PCI_Express_CEM_1.1.pdf

See figures on pages 58, 59, 72-86. IIRC, the ATX specification linked above shows the physical layout of the motherboard which may be helpful with some of these figures.
There are also sketchup models of compliant single- and double-slot cards in the Resources section of SFFN.