A-Rama or O-Rama?

Help me out here. Is it “a-rama” or “o-rama?” (For example, your favorite local skating rink might be called either “Skate-A-Rama” or “Skate-O-Rama.”)

Ty suggested the following very possible scenario: a business moves into town, chooses their -vowel- wisely, and proceeds to set up shop. After a short amount of time, a second business owner decides the local economy can support a little friendly competition and, lacking the skills and/or monetary resources necessary to create or procure an original name for their new business venture, simply chooses a different vowel instead. 

(Hopefully said vowel choice is not e, i, u, or sometimes y. After all, Skate-U-Rama doesn’t work very well and Skate-Y-Rama is more than likely bad Spanglish.)

I don’t buy Random House’s explanation.