Jim
thanks for your advice. could you clarify... ??

1) since the plane is a trainer .... there is already one tank in the fuselage . as per your explanation this tank is # ?? ( 1 or 2 )

2) the strapped on tank will be above this tank so this is tank # ?? ( 1 or 2 )

so the top tank should empty into the lower tank ??
fuel draw is from lower tank to carb .
muffler pressure is in top tank.

the connecting line from top tank .....
should i use long line in the tank with clunk ( like in normal fuel tank) ... and in the receiving tank below use short tubing at high position in the tank say like for muffler pressure position.

will there be any potential problems in muffler pressure .... enough for both tanks?? assuming no leaks...

thanks again.