fill tube dia?

[55metalmonkey]

Just looking for some input for a fill tube dia. generally I stick with a stock size but this situation is a little different.
I'm going to put a fuel door on the right side fender out of a 80's van like a few other guys have done, this will have the fill and a vent line but it is going to a RCI poly fuel cell. it's a top fill style so I will have to make a new plate for the top and extend a full tube over to the fill door.

I would like to keep the tank as high as possible so after all that bla bla bla the question is : does anyone have any idea on what the minimum recomended tube size would be for the fuel fill tube? I know bigger= better but in this case the smaller the tighter radius bend I can get. I don't want to have the issue of the fuel tipping the stop on the gas pump everytime I fill up. IMO 1.25" looks to be the min but if anyone has done it with smaller and didn't have a problem I'd like to know.

Thanks