adjustable alley help

[Tbrake]

I am currently in the process of building an adjustable Alley. I started off not planning on making it adjustable, but stupid me changed my mind half way through. Going to cause a lot more work than was needed. I am having trouble figuring out how the rear gate on the adjustable side is going to work. I am planning on making it similar to gobobs alley in this link
http://gobobpipe.com/cattle-working-equ ... ttle-Alley
I have looked for hours online for pictures that will help me, and nothing has. The front gate will be easy, but I can't picture how the rear gate will work. Only local ones I can find to look at are the junk bolt together kind. Anyone have any pictures that could help me out? Here is what I am working with. It's going to have swing open emergency gates on the left side. Sheeted 48" on both sides. What should be my maximum width and minimum? I was thinking 32"-18". Will be working heavy breds, down to 5-6 weights. Any help or suggestions are greatly appreciated.

 

[bird dog]

I built mine a few months back and left where they enter at full width but with a pivot pen. I am using 3 alley frames. Mine is in two 10' sections with the first section more like a funnel when I narrow it down. The second section completely narrows down. They are separated with a sliding gate. Occasionally one will turn around in the widest part of the funnel but it has not really been an issue. My adjustable alley frames are some real old priefert frames I bought off Craigslist and kind of modified to fit what I wanted. They go from 28" to 18"
I don't have emergency exit gates but the panels I use just sit in a bracket with a chain to secure it. It could be taken apart fairly easily in an emergency.

 

[Tbrake]

Thank you. Anyone else?