RE: Improving stability
I went with the Guardian myself, and man is it fun. I bought it to tame my Stearman down on the takeoff roll, but decided to try it out in my foami first.
It's about a pound and an half and really bounces around in the wind. I put the guardian in, flipped the switch and it was like the wind stopped. I was amazed at how well it works. I just ordered another from Tower Hobbies because now I'm having so much fun with it in the foam airplane, I don't want to take it out.
The nice thing about the guardian is that it is not gyro based. It works off an accelerometer and it has tons of settings if you want to get into really fine tuning it with your computer. You don't need to do anything with the computer at all though if you don't have one or don't want to. You can program settings through your transmitter. It's very simple to use right out of the box though. You plug the aileron, rudder and elevator servo leads into the guardian. Plug the leads out of the guardian into the receiver. Mount the unit so it doesn't move and your pretty much ready to go. You just have to check direction on control movements to make sure they are correct and turn the gain up on the unit. I found the hard part, to be mapping the Aux and gear channel from the receiver to a three way switch and slider on the transmitter. Not that it's hard, but I'm kind of a dumb #%$ when it comes to technical stuff. I asked a question on a forum and had my answer.
You can fly your plane around with the unit turned off if you like, flip a switch, and have it on. The switch has what they call a 2D mode and a 3D mode, it helps keep the wings level in 2D and if you get into an unusual attitude, just let go of the sticks and it's flying straight and level again. Personally, I have been flying for years and don't care to use that feature. I don't feel I need it and really don't care much for it. I'm am however amazed with the 3D feature. I like doing rolls, loops and flying 3D which includes the harriers, torque rolls, etc. This is where the guardian really shines in my opinion. Since you can control the gain with the slider, you can turn it down or off and fly around fairly fast doing your loops and stuff. (Having the gain turned up too high and flying fast will result in oscillation if you didn't take the time to dial it in, very easy to do though.) Then slow the airplane up, turn the gain up and bring the plane down doing an elevator, no wing rock at all. Transition right into a harrier and steer it around using only the rudder. (Having heading hold feature on, you can use the rudder all you want and still have the airplane locked into your last attitude, but touch the elevator or ailerons you you unlock all three axis until you center the sticks again, pretty cool.) You can even take your hands off the transmitter. It feels almost like that's cheating though, so I disconnect the heading hold feature using the computer and you still get the benefits of having stability, but you still have to fly the plane. It counteracts all wind and gust trying to throw your airplane around. It makes flying in all wind conditions like there is no wind at all with the plane feeling like it also perfectly setup.
After all, this hobby is all about FUN, and that's what this Guardian does. It lets you have more fun than you have experienced in the past. I feel once everyone checks one out, it's going to turn into the future of RC!