No problems at all:
well I dit it like this:
I have it installed with the 2 sides of the tank connected on the vent hose of the main thank.
The hose is also over the dashboard so I can fill the tank with the petcocks open and he do not overfill the main thank.
The advantages are:
-petcocks always open,
-no drilling in to the main tank.
- not possible to overfill the main thank
Last year i have driven this system with a jerrycan for 10000km an it works perfect, when the main tank lowers it sucks the gasoline from the jerrycan, now the tt-tank.