Welcome Mike D! I didn't have lip cancer, but tonsil located in the oropharynx, which has some aspects in common with lip cancer. What do your doctors think since you're considering radiation? 1-5mm are close margins, and greater than 5mm are clear margins, and less than 1mm are positive margins, so you're right on the line with 1mm. Surgery alone is often the treatment with T1 tumors, like you had, but negative prognostics, can change that and need for radiation. With lip cancers brachytherapy, an internal radiation, can be done at facilities that have experience with it or IMRT, a common form of external beam radiation.
Below are the NCCN Guidelines for Head and Neck Cancer, which include lip cancer, that had its own treatment guideline. These are 2013 Guidelines so if you want the 2015 update you'll have to register to the NCCN sight. Not many changes
occur year to year, but I don't often look in this section to say what was.
As mentioned, no harm in getting a 2nd opinion, and most often many patients are glad they did, even often times staying with who they originally saw, but sometimes not, and that's good too.
http://oralcancerfoundation.org/treatment/pdf/head-and-neck.pdfGood luck.
