Yeah k4bb, 3 stitches isn't enough to prevent sides from curling. And even 5 stitches can look like it wants to curl in, if you know what I mean. Even if it stays in place, the stockinette can look puckered, like it's trying to curl.
Stockinette's tendency to curl is VERY strong. I personally tend to just avoid stockinette altogether for scarves, unless it's knit in the round.
If you like the stockinette look, a similar effect is to make a scarf in k1p1 ribbing. It lays flat and looks very stockinette-ish, since it contracts and you end up looking at all V's. Rather like a reversible stockinette. But you have to like working in ribbing, or want to get good practice at it.
KnittingHelp Queen Bee
It is not because things are so difficult that we do not dare; it is because we do not dare that they are difficult.