Adrian,
I have used the pleated paper clunk sold by Mick Reeves for my JetCat P-80 and it is great.
It does not fit into a Dubro or Sullivan tank.
However I made a fuel tank from a 2500 ml bottle, laid on its side, on my test stand. The engine, at full power, drew pure fuel without bubbles until there was only 2- 3 mm depth of fuel in the tank. Using the felt clunk it started to draw bubbles at full power when the felt clunk was half exposed.

For my P-80 powered Rookie I used a fuel tank made from a 2 litre cider bottle and a Mick Reeves pleated paper clunk. No UAT, just straight from the tank to the pump. It has been perfect for over 100 flights. Not a single flame-out related to fuel feed (one due to faulty electrical connection).

On my Boomerang (Wren 54 with Dubro tank, felt pickup, plus BVM UAT) I did experience 2 or 3 unexplained flame-outs, by the way.