Here’s a quick work around that I use. If your clip is in the primary storyline, just select the clip, hit Command, Option, Up Arrow to temporarily move it up as a connected clip. Then adjust your retiming and correct duration that you want so it fits back in your primary storyline the way that you want it. When you’re ready just hit Command, Option, Down Arrow to move it back down to the primary storyline. It’s a pretty fast way to do it without screwing up the timeline. If any one knows of another way, I’d like to know too. Hope that helped!