Wedging in a piece of styrofoam will hold the battery fine. And adding 2oz of tail weight is not big deal at all and won't hurt your airplane at all. Good luck when you get it all set up and ready to maiden.

She flew today!!! Everything went perfect! I must admit I am going to have to agree with those that say you should have and experienced pilot help a newbie to fly. A couple of guys from the local club helped me out and I am really glad they did. While the balance was perfect one of my servos needed to be reversed and I didn't have the prop nut on tight enough. They were also indispensable in getting the engine tuned properly. Thanks Roger and Shane!

"http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXZ653&P=7"
I have that muffler and it is great. I also had the tower trainer as my first plane, its a great plane and very forgiving. Also as far as GC is concerned remember its OK to be a little nose heavy, but never tail heavy. By the way, I used an O.S. 46 and it was almost spot on.
Glad to hear it flew. I bet it was your elevator servo that was reversed wasnt it? I did the same thing when I was building that plane.

I will throw this out there: I like to have my students balance their trainers a little nose heavy, 5-8 degrees down when held at balance point. This helps in making the plane more stable in the air and makes the glide path on landings a little easier to manage. The planes tend to float less when landing. Just something I picked up years ago in RCM. I think problem here is the ST engine. I quit using them when the engine blocks are machined from a block of aluminum and that ugly heavy muffler went on. It is one of the heaviest engines out there.

Congratulations on the first flight of your first model!!!!

I wish you many more of both.[sm=thumbs_up.gif]

Stay open to advice, keep asking questions, practice much, be safe and courteous on the ground and in the air.