Is anyone else a little skeptical about balancing this plane with a full tank of fuel as per instructions? I had to add 5 ounces of tail weight to get it to balance at 5".

That manual is the most worthless POS I've ever seen.
DO NOT set your CG with fuel in the tank or you'll be very tail heavy at the end of a flight.
If you don't own a CG Machine or know someone who does. Here is an easy way to get a decent and safe CG setting for your first few flights until you think you might need more balance towards the tail.

Start out with an EMPTY FUEL TANK.
Plane upside down or rightside up. (Doesn't matter as much with a mid-wing acrobat like an Edge540 or in this case,,, SS120. I balance my mid-winged planes rightside up.
Feel along the wing for the main spar that runs from the root to the tip. Place your index finger on or just ahead of the spar closest to the fuse and lift your plane. Move rx gear or add weight so that it balances or slightly falls forward towards the nose.
Better to maiden nose heavy than tail heavy any day.

Yes, I have the cg machine, and I typically balance my planes right on the spar with tank empty. I was/am skeptical about balancing with fuel in the tank. Ugh.

i just checked mine for ya twister, it flies great at 4.25 behind leading edge

Thank you Gary, that's where I will set it to right now.

Mine is CG'd about the same as Gary's. Flys great and will do killer flat spins.

Ok, got it balanced last night at 4 3/8" by putting the battery over the tank, and 2 ounces of lead under the tank. Thanks guys, we'll see how she does.

let us know