Roland,
Just wanted to let you know that last night I moved my battery and and receiver (small Futaba 2.4) as far back as I could in order to balance. But, not as far as I would have liked. I still had to add 1/4 oz weight to the tail in order to get it to balance at 4 3/4". I could have left my receiver in area were the plans say to install and hold in place with balsa sticks. With my receiver in the location shown in the plans, my battery needed to be installed RIGHT were the elevator and rudder servos are. So instead, I put the battery under the servo tray, right up next to the throttle servo, and mounted the receiver to the balsa peice that is the back side of control panel. The reason I am telling you all this (even though you asked about flex rods) is because moving to a single servo in the tail and joining the elevator halves sounds like a real good idea. I wish I thought of that! That would leave you with a lot more room to move the battery and receiver around for proper balancing. Also, I haven't checked into this yet, but since I am using the OS55 with a bisson muffler, alum back spinner, and MAS 13 x 6 prop, I probably have more nose weight than the plane was designed for. Hope this helps.