well.. as of now... or before even.. by following the instructions the following was achieved: The clunk does not move down by lowering the tank vertically... it will move down.. if I wip(and i really mean "WIP") the tank downwards.. the momentum will move the clunk down...it'll take less of a wip upwards to bring the clunk back... so even before my questions in this thread.. i had everything correctly...

what i'm trying to say is that it'll not move but it self.. but rather with a big wip downwards...

I would put a brass tube in as you guys mentioned.. but i don't have the material at hand.. and i really believe that it won't move down by it self...

i also noticed.. than you can check if the clunk is in the right position by tilting your plane left and right.. you should hear clearly the clunk hitting the left and right sides of the tank... i'll prob do that everytime before each flight.

thanks MinnFlyer for that pic.. your illustrations are very helpfull....

thanks to all for your great responces...