I know you won't have problems with just the two. Adding the third hose to fill from another shouldn't be a problem if (A) the tank vent is high enough so the fuel coming from the other tank doesn't back up and come out the vent. (B) If you have the engine running and returning fuel at the same time that the fuel transfer is taking place from the other tank and you don't over power the diameter of the fitting into the tank causing it to back up into or out of the vent line.