RE: Felt Clunk problems?
I suppose it's 'horses for courses' though I would not think a few extra ounces would make that much difference to wing loading/performance unless slow flying is important say because of runway restrictions. Having said that I have used a pleated paper clunk in my fuelling rig and it does seem to work well though the 'neck' of any airframe mounted fuel tank would severely restrict the choice of suitable comercial tanks.
Rob.