4 1/2 inches and I am going to try to ease it back from there a little at a time. My friend (lovemyedge) has the lanier edge and he says his is just over five inches, and is still very stable. So I think the 4 1/2 is conservative. A heavy plane will fly poorly and act unstable, they like to snap easier. So see if you have any weight you can remove. Also did you balance yours upside down? I did, and I think thats how you are supposed to do it. I have had several "scale" areobats and have always balanced upside down. I don't know how much experience you have with these planes but they do not have the flying characteristics of many sport planes. They just aren't as forgiving. Hope this helps. Happy flying