I'm running two Yellow Aircraft saddle tanks in a Wren 44 size aircraft. The clunks will swing from top to bottom ok but will not drop forward when in nose down attitude.I'm using yellow tygon supplied with engine. 4mm? Is there a more flexible tubing, or just need a heavier clunk.Would orbit work and where can you get them? DB

This was the issue with the tanks in the L39's. On approach, fuel would rush to the front of the tank, starving the engine, and inducing a flameout on finals (not the best situ!) I cannot advise about tubing etc.... but many solved the problem by using tanks that keep the fuel deep and in the grasp of the clunk. I presume a UAT/header type tank would also solve the problem. Do you have room for a header tank? how's things progressing with your A4?
D

(more experienced people, please correct me if the above is wrong)

I wouldn't be too worried about that. In fact, on my latest tank (2.6 litre) I have spent a fair amount of time stopping the clunk falling forward.

The yellow tanks are narrow and tall so I can't see it being a problem.

BVM sells some extremely flexible clunk tubing

Fuel line (36") BVM #2804 $5.00

Thanks gentlemen, all good info. DB Gravity is relentless!!!!!

Just remember, if the clunk is allowed to go forward it could get stuck forward and flame out the engine nose high. Might be best overall to use a header.