Awrighty then, good question, I forgot that I read about your dilemma before I finished mine.
Turn your fuse over and look at the aft wing saddle where the yellow meets the red....peel the yellow and the red back (don't worry, Ultra coat will iron right back down) exposing the 3 1/3 X 4 1/2 piece of balsa between the saddle and the stick fuse.

Slide your #11 blade under the balsa between the fuse and open it up....now, the bottom of the rear canopy is exposed lay your battery on that shelf...directly under the turtle deck, it will fit perfectly, and there is a lip on the back AND front to keep the battery from sliding back into the fuse. Now, CA two sticks, Popsicle or balsa right on top of the battery, holding it in place PERMANENTLY until you crash or start a cutting. I'm using a 6V batt for faster servo time and much more tork.
CA the bottom back on and iron the covering back where it was...this operation takes exactly 10 mins...Voila, absolutely spot on CG and you cannot tell you were ever there with a #11....takes just a breath of down when inverted.
I'll take a pic when I get home., but when you look at it you'll see..remember the battery is not on the bottom of the fuse, but the top, right under the forward turtle deck, on the provided shelf.

I hope this helps and good luck,
Mike