I changed most of my Flyer style couplers to the scale sized ones. Since I run passenger trains as a unit, I don't care if the couplers uncouple or not. I've been able to bend the Delrin scale sized couplers quite a bit to correct any sag and align them better. The Flyer ones can also be bent along the arm to raise them. I've done it without breaking them. Dont be too afraid of breaking the arm. The plastic is tough. Just try a little at a time.
I do the same. I have plenty of tight curves and curves on grade, and yet I have been able to get all of my AM Budd cars and heavyweights to stay coupled with their non operating scale couplers.