There has to be a way to force DropStuff 10 to make normal .sit files (or .hqx for that matter) that will open with older versions of Stuffit, than just the .sitx that only open in OS X.
Magic Menu--If you have Stuffit Deluxe--and you do--then this little utility should be running. If not, launch it and it will add a menu to your icon bar. If you want to archive a file or folder, click on the object to be archived.
Choose Magic Menu (icon) > Archive > Stuff (.sit).
Alternatively, you may choose the .sit format as your default:
Choose Magic Menu (icon) >Preferences.
Click the Stuffit icon.
Select Stuffit from the popup menu.
Click OK.
Now if you want to archive a file or folder:
Click the object to be archived.
Choose the Magic Menu (menu) > Stuff menu item. This creates an archive in the Stuffit (.sit) format.