Replying to Line chronic wide question???

ok so this may be a really stupid question, but i ordered 177cm chronic wides off of evogear, and when they got here they said 177 on the tail and everything, but they seemed shorter than my previously owned 176 ar5s. So i measured them and from tip to tail they are about 172 cms...Im not sure if Line just runs shoter in length or what, but they seem short for 177s. so my question is, when your measuring your skis, do you measure from tip 2 tail or by the running surface of the skis, excluding where the tips start to curve up? thanks a bunch