I have the hardest time with this for some odd reason, my farl blueprint is the default one but it will only lay one rail , not both, either going north and south or east and west.

The default blueprints work fine for me. Put 2 empty blueprints in your toolbar, get in a farl, click the Settings button (S), click "Vertical", "Diagonal" and then "Read", save the settings (or get out and back in the farl to close the window), click Start and it should be fine.

Edit: if you are mojo2012 on github feel free to reply there, better chances of me noticing it xD