Do Hayes Tanks work well without pressure?

I used one with a Fox 35 and pressure and it was a great run, but I would like to use one with and LA 40, a McCoy 19 and an FP 25, all possibly without pressure.  If it works, what should I do with the top vent?

I have run Hayes tanks without pressure with good results.  I usually cap the lower vent to keep fuel from running out and leave the top one open.  On one plane I ran a line from the top vent to the hollow in the backplate of the engine to help with upwind and downwind pressure changes. It isn't connected to the engine, just tucked into a dead air space. Uncap the lower vent to fuel. 

"What do you mean by "the top vent"?     Maybe I should have used a different word than "vent". 

The Hayes tank is a molded plastic tank with three openings stacked vertically.  The bottom one goes to the clunk and is the fuel feed.  The next one up is the fill line and is capped for operation.  The top one can be connected to pressure and is the overflow, air escape vent.  I have found that I need to stand the plane on it's tail to fuel.  With these tanks, there is not the bother of getting three tubes correct in the rubber stopper.  I know a lot of people like them for profiles. I do. However, they are discontinued.  I just ordered a 3 oz. and a 4 oz.  They were the last ones that company had. 

Another question:   would putting a copper tube face forward make a quasi pressure and have any positive effect?