Technically there is no problem. But my apprehension is that if yours is a ticket for reservation and if you change the boarding station and opt not to board from the boarding station printed on your ticket, the TTE, when he finds that your berth is vacant, may allot it to some RAC ticket holder. And when you board the train from the next station or any station after that, you may find your seat occupied. I may be wrong. I would like to request Dipyaman sir to correct me if I am wrong. Thank you.