If the guy in the mirror says it's ok, then wear it. Personally I'm not big on the "t-shirt under the polo shirt" look. It's like wearing two like shirt, one on top of the other. If, because it is white, you are portraing it as "underwear", (I do wear a "V" neck t-shirt under a dress or sport shirt. I also live in the south!); then, why would you want to show off your underwear?

Like I said, if you like it, then wear it. I just give you my opinion. Probably wont be shared by many. I think my age is showing.