For that size plane, you should add the necessary weight to bring the CG to the recommended point. On a large quarter scale plane, it is not uncommon to have to add a large amount of nose weight to get the CG in the proper place. I've seen some that required in excess of two pounds. If you try to fly it tail heavy, it will probably be it's one and only flight as it will be very hard to control. It is always better to rearrange the internal equipment to bring the CG into it's proper place but is sometimes hard to do. From your comments, I am assuming you are not a skilled flyer. If my assumption is correct, I'd highly recommend that you get an experienced pilot to give you a hand and to make the first flights.