I ordered This dock extender and it made my current Sony alarm clock radio "compatible". You will need to order the "slim" so that it will fit the Otterbox, but with that .. i'm sure 99.999999% of all the docks will then fit.
For my Sony Clock/Dock, it has an adjustable "back rest" that relieves some weight/pressure. i don't believe the weight is enough to cause a problem because the dock extender only adds about an extra 1" and is pretty sturdy.
I just received the Sonjimoru dock/cradle and it works with my Otterbox Defender case for iPhone 4. I used the whites standard apply cable, connected to a USB port on CC and it syncs and charges!