I don't know how the Chubby's are set up with the outlet but perhaps you could do a modification like the one made to a standard Windsor outlet neck I am now using.
Can't remember who gave this to me from within the cobra community but it does make the cap the highest point on the motor.
This means it is also rigidly located compared to the in-line type fitting you pictured. I know this as I had a moroso variant in use initially and the assembly would push down on the attaching hoses when trying to refit the radiator cap.
Just went looking and here is a picture of it in-situ now, though I've replaced the overflow barb with dash fittings and braid line to the overflow tank now.
Just a thought.
Cheers