most twin tipped skis have the center or 0 mark at the traditional mounting point, and then additional lines for +1, 2, 3, 4 cm forward. others have their 0 mark at core center. if they are mounted at core center, like a true twin tip, and there are no other markings, i would contact the ski maker and ask them. they sometimes design the core of the skis around where the bindings will be mounted. mounting beyond this point, you could risk pulling the bindings out. i would still like to see a picture of the mount. and if you were only going to be doing normal alpine skiing, with no halfpipe or need for twin tips, then why would you buy these skis? any decent shop will set you up with the right equipment for your needs and ability. you basically bought a car, to do a 4x4's job. and if there are normal mount markings on a ski, i find it very hard for a technician to mis-mount them. in my 15 yrs on the job, ive never mis-mounted a pair of twin tip skis. we always make sure we have both tips facing left and verify with the customer and on the ski, where to mount it. if there are no distinguishable markings, we contact the manufacturer for measurements. if they are indeed mounted at core center, you may need to call them to see if the structure of the ski can handle being mounted back at a traditional point and how many cm back from the tip that should be. if the ski wasnt designed to be mounted that way, they may ski like crap.