I found my answer by using search from an August 6, 2007 thread started by John Miller.  I was able to print off his drawings.  The overflow is up very close to to the top edge the tank as mounted.  He says there's an advantage in using these tanks.  Instead of adjusting the tank up and down to get the right orientation with the engine, one just turns the placement of the cap with the three tubes to adjust the apparent height of the uniflow tube to bring about the best orientation with the engine and it works well for stunt.  Interesting!  I will be trying this. It's a very interesting thread.

Allen Eshleman

Here's a nice site that explains everything...

http://home.cogeco.ca/~controlline/tip1.shtml

I realize there are a lot of tanks set up with the uniflow linked to the pickup on a clunk tanks.   I'm wondering if that might be a reason for some mixed reports regarding how well plastic tanks work for stunt?

As I see it, if you tie the uniflow to the clunk, every time the clunk moves, your relative fuel head changes, and therefor, your run also changes. The whole deal with a uniflow is that where the end is, inside the tank, is the place the system sees as the center of the tank. If it's moving, then the center of your tank is also moving. It may be hard to get a really good run with that happening.

By routing the uniflow, by itself, to the inside wall of the tank, the uniflow referance does not change when the pick up moves. A better solution that should give true uniflow performance to a plastic tank.

I've posted it before, but here's a jpeg of a drawing I did that shows how to set up this style of clunk tank.

I agree with John Miller. I don't see how the uniflow tied to the clunk can possibly work well.  I have watched airplanes with the tank set up this way fly, and the engine run is as good as one could ask.  However,  given my strongly held beliefs, I am sure it would not work for me.