I made the trek to my LBS. His opinion is that spinning the peddles (backwards) does not alway yield valid results. However, we added a little nut to a longer B-screw and that has taken away the noise and potential for the cog to hit the sprocket.

As pointed out by Trucker Dan, it's very possible that the problem has been there all along, as the 12-27 combo is a challenge for the short cage. I may have never noticed, as I've never done anything to this drive chain except lube. The bike came with a standard set of chainrings and a 11-25 and I upgraded to a 50-34 and 12-27 for the extreme hills in my neighborhood.

I guess as long as it all shifts well and doesn't make bad sounds I should be alright. I appreciate all the helpful advice and posts here.

I would be curious to know if anyone else has a similar set up on a Tarmac SL3 and had the same issues.