Yo I have 2009 rossi S3's 177 they are 98 underfoot and 127 at the tip. So I bought G3 climbing skins 171-181 in length and 130 in width to cover the tip. They come with a trimming tool and its super easy. The skins I got arnt the twin tip ones so I just put the strap on the back like a regular ski and duck taped it. On the box for the skins it has all the diferent size measurments to fit the ski and evrything is pretty much fool proof.
hope this helped
Oh ya and you dont have to have the skins the same width as the ski. It depends how steep your terain is. If its steep you want more skin surface on your ski, if its not so steep you want less. Just think of the perfect balance for you.
And on the box for my skins it says you can get X-long 189-199 and 140 in width is the biggest!