See now this statement only makes sense to me if you have a really beat in straight to understable firebird and an overstable teebird. But your statement to me says that a firebird will stay straighter longer then a teebird and I dont quite agree with that.
Yeah, you're looking at the word stable to mean straight, and my whole argument is that discs don't have absolute flight characteristics. You can only compare them to each other on a spectrum. See like the incredible hulk would not find any discs that are "stable" in the straight sense, but he would find some discs more stable than others, as in "more resistant to turning over."
The way I'm trying to explain this is also consistent with the way nearly every pro player talks. When they say that something is stable, they don't mean it flies dead straight almost ever. They are saying that it wont turn over easily. That's what a "super stable" disc would mean. You could call it overstable, and I'd know what you mean, but overstable is only going to be relative to how much power you have, and it doesn't tell me anything about the disc. My 5 year old daughter finds the Comet to be pretty overstable.