The Line Invader is an entirely symetrical ski both in DIMENSIONS and in FLEX PATTERN meaning both dimensions in tip and tail are identical as well as stiffness and flex of the tip and tail.
Because of this, you can virtually mount the ski in any direction you choose. I have my 08/09 Invaders mounted with opposing graphics as well (One up, one down).
However, if your skis were symmetrical dimensions but NOT symmetrical flex pattern, you could not do this do to differing stiffness in tail and tip. Some Symmetrical skis on the market don't have symmetrical flex patterns just FYI.