I have not read Gorr,s book, but the horizontal mark he's talking about is probably on the plastic float itself (the seam?), and yes it should be parallel with the carb body. If you're holding carb upside down and the floats are shooting upward at a 20-30 degree angle when lightly seated on needle then yes, float level is too low. Also make sure carb is clean. Take jets out, clean everything with solvent, & blow jets & ports out w/ compressed air. If there is one grain of sand stuck in a jet, it will effectively decrease jet size.