My SFGs are a little off. Also, they are not exactly straight up and down. I have to trim the plane differnently when I use them but it doesn't seem to be a problem. Also, I definetly try to keep the speed lower when I fly with them, but I haven't noticed flutter with them on but I'm pretty cautious with them on about speed. They are designed to help the plane in slow manuevers so that's how I use them. They sure make the plane fun though. But I enjoy flying it without them also. And I think you better get good at repairing them, I've already had to repair one.
Thanks
Barry