I went through this in June 2011, also to match my CO and UA accounts (no middle initial on UA). I emailed CO to drop the middle initial, they emailed back "Your request to modify the name on your OnePass account must be accompanied by legal documentation. Please mail a copy of your government-issued identification such as a passport, driver’s license or birth certificate"

I simply emailed back, saying literally "I wish to DROP the middle initial. There should be no need for documentation for that."

That did the trick. I never heard back from them, but a few days later they dropped the middle initial.

I hope this helps.