Hey guys, sorry if this is posted in the wrong area.

I have a Great Planes Big Stick .40 with an O.S. Max .40 LA engine. (9.5 oz). I am going to install a Tower Hobbies .46 (16.9 oz).
Do I mount this engine further back on the mount or in the same place? Also will I have to add alot of weight to the rear of my plane? What other problems should I expect?

Thanks