I understand your dilema. I had DaVinci in 2005 (positive margin) and my psa stayed undetectable (<0.1) for about 5 years when it started creeping up. It hit .07 in August 2011, six years from my operation. I began studying supplements that had been shown to have an effect on PCa. In February 2012 psa hit 0.11 and my uro encouraged me to consult with a radiation lab. I had heard so many horror stories about the side effects of SRT, along with the idea of going in 5 days a week for 7+ weeks, that I decided to postpone SRT as long as I could so began a supplementation program in earnest.
Don't know if any of the supplements I take are responsible. And, even if they are, I have no way of knowing which ones, if any, are working. What I do know is that as of a couple weeks ago my psa was 0.12, nearly 2 years since it was 0.11. The doubling time is many years.
I have been very fortunate in that I have had zero issues from my prostatectomy and, at 66 y.o., am fit, active and in very good health. As such I am in absolutely no rush to jeaopordize that with radiation. Even my uro agrees now and has gone back to 6 month psa checks.
Of course if my psa begins to accelerate at some point I will have to reconsider my position. In the meantime I will spend stupid money on my supplements and enjoy my good health. Of course my hope is that my psa will remain low forever or, at worst case, continue to rise at it's current leisurely pace. Another factor in play is that the longer we are able to put off treatment, the more advances that are being made. My uro told me the other day that there are some incredible improvements in the works for SRT. Could even be that, with more precise targeting and dosage control, the nuber of days required for treatment will be drastically reduced.
I know our cases are not identical but thought you might glean something from my journey. Good luck.