At our resort we never had any problems with the twin line tanks except for customers forgetting to loosen the cap.The odd time one would leak threw the carb into the boat after coming back to a gassy boat they usualy remembered to lossen the cap.
WE had many single line tanks that would build pressure we always ran them cracked open.
In 49 years I do not recall one twin line tank failure except for worn connectors
I probably changed a couple dozen fuel pumps.When I was around 12 years old it took me awhile to figure out why the 9.5 johnson kept fouling the top plug bad fuel pump gasket I made a new one out of an old time rain suit.Good lesson learned
