DropStuff must be set up right. Here's how to do it.
Step 1. Open DropStuff and then open the preferences window, it looks like this
Step 2. In the archive type menu choose Stuffit X
Step 3. In the compression level choose Custom...
Step 4. A window should open, if it does not open then click the Settings button. the window looks like this
Step 5. For compression method choose "choose method by analysis"
Step 6. slide the memory consumption to 25
Step 7. turn redundency level off
Step 8. turn encoding off
Step 9. turn optimizers ON
Step 10. turn blockmode ON
Step 11. click the Stuffit5 tab
Step 12. The stuffit5 panel should have one menu called compression method. choose the "choose method by analysis" choice
Step 13. Press OK
Step 14. Press OK on the other window
Step 15. Stuff your files!!! They should be smaller now, but it takes a long time to stuff.
Modified 16-Nov-2015 to fix the images.