Hi Bob and welcome to the forum. This is a great community of folks...
My case was a lot like yours (though remember we all respond differently to treatment). I was T1-2 N0 M0, with a well-differentiated tumor. I had my tongue mass (2 cm) removed in October, and a PET scan taken about five weeks later showed no signs of cancer anywhere.
I debated the radiation thing since they said I was 50-50 on needing it. But finally on the advice of both of my docs (who said they WOULD do it in my case) took the plunge and did six weeks of IMRT treatments. They hit my mouth pretty hard as well as both sides of my neck. That was back in December and Jan.
Well, in May it was discovered I had a recurrence in one of my lymph nodes (on the same side as my tongue cancer -- the left side). Apparently for a reason I'm still not sure of, they chose not to radiate that part of my neck so somehow some cancer cells snuck away from the original tumor and made their home there. The rest of my mouth and neck (the parts they did radiate) are clean as far as I know.
Anyway, I say this so you know that tongue cancer can be a feisty foe and even with radiation it can come back. If I had it to do over again, I would go through radiation again but I would first have gone to a comprenhensive cancer center for a second opinion on how to do it. Maybe IMRT wasn't such a good idea? Who knows... I can only speculate now...
Good luck to you -- we all pray for you that you'll give your cancer the death blow the first time... Don't be afraid of getting second and third opinions. Be as aggressive as you can be now -- your best shot is knocking it out in round one...