I've owned the 20” Westcott Rapid box for a while now and I've had a few issues with it here and there but think I've found a reasonable way to improve it.
Often I find that I like the “liquid wrap” effect that is produced by placing a beauty dish close to the face of a subject. It is a great beauty look which is one of the reasons that the beauty dish is called what it is.
This image was taken using a 22” Paul C. Buff Beauty Dish and the Einstein light and shows the type of look that I'm going for when I say “liquid wrap” effect.
I've found that no matter which way you install the deflector disc you end up with a harsh shadow in the center of the light pattern. Its also unclear which way to mount it because there are actual Westcott images through out their web site showing it in both orientations.
First I tried putting the disc on with the cup pointing backward toward the speedlight:
As you can see this results in a harsh shadow in the middle of the light pattern and you can see some striations from the umbrella elements in the modifier.
Turning the disc around to point the other way gives the same effect but as you would imagine the shadow is just a tiny bit smaller than before.
For the lonest time the only solution I could figure out to improve this situation was to add the diffuser sock onto the front. But this really doesn't so much make it a beauty dish any more. Its more of a very small octabox at that point in time.