Welcome to the forum, Chris!
Actually, for that system, the tall speakers are the rear speakers - and the smaller speakers are the front speakers. So, you're all set.
Adam
EDIT: For reference, you can check out the owner's manual at the link
here. It shows a diagram of the system on page 13.
BTW, the front and rear speakers used the same size drivers and have the same frequency response, so I would think that they would be interchangeable. So, put the tall ones in back or the front, whichever you prefer.