My new to me Optimus 11 runs but poorly. I have freshened the cap gasket and PIP. The pump works but requires way too much force. Removed the pump as a unit. The leather cup that was fitted is way to big for the stove. No way I can ever git the cup back in the stove. The cup must have been bone dry when it was 1st fitted than oiled which swelled the leather. The 11 has the pump next to the fuel fill port. The rod is shorter but similar in design to the latter 111 stoves that have the pump in the end of the fuel tank. I have tried the 111 cup and several others that I have on hand. They were all 2 large and in my opinion 2 thick. Anyone know for sure what I need. Or maybe there's a secret to fitting pump cups that I never learned. Thanks.