It doesn't matter which way around the lenses are or which one goes first. Using Gullstrand's Equation I calculate if you hold a 0.5 dioptre lens 11.9225cm in front of a -0.5 dioptre lens the resultant focal length is 335.50010 cm.; which is what you want. A more compact assembly is possible if you use powers greater than +/- 0.5D.