One thing to consider is that if the uniflo tube is too close to the pickup clunk air bubbles may pass directly from the uniflo to the pickup and create a lean condition. Personally I think 1/4 inch is not nearly enough distance between the two terminations. I never use less than 1/2 inch and sometimes a little more.
Mine are typically within 1/8" with no issues. I solder the vent tube right into the wedge of the tank, to within about 3/16" from the rear, then run the pickup along it, with a bend in the very end of it to get it as far back and as far into the wedge as possible, so I have to put a little 1/4" or so "kick" in the end of the tube. That's why they run the same to nearly the last drop everything, with no changes in the mixture until it is ready to run out.
In the air, the last place the air wants to go is sideways (relative to the local acceleration) into the pickup. It might make some difference on the ground but I haven't had any issues with that, either.
I have used a rigid uniflow pickup in a clunk tank many times in the past. The vent has to end up along the outside edge of the tank, but the fore-aft position doesn't seem to matter, as long as it doesn't interfere with the clunk movement. If you try to make the vent move with the clunk, you need a slip/sliding fit for the vent so the vent and clunk lines can move relative to each other. Otherwise the clunk will not move freely enough. I have tried separate clunks, but the chances of them interfering with each other is pretty high.
I don't like clunk tanks very much because the cutoff is usually terrible. The round or flattened-ellipse type (similar to Billy's shampoo bottle tank) are generally better but I doubt that the clunk actually moves very much, with makes it more reliable. I haven't seen the elliptical type in a long time, and I don't know if they make them any more.