I think the OP means a "sternum strap" NOT between two shoulder straps, but passing under the armpits from the pack across your chest, and back to your pack.
Limiting ourselves only to men and flat-chested women, I still see a problem.
You breath. So your chest strap would loosen 1.5" on every exhale. You can't use elastic if you want it to hold any weight, so the pack would sag back every 5 seconds. Maybe that's okay. It would be easy to mock it up and test.
Also consider a "trump line" to avoid the shoulder straps. The height and the angle might be better, especially if it came off the very top of a tallish pack.
That's an extreme example, but maybe shows its potential.