Hi Tom,
Sorry you had to join us at a young age but welcome anyway.
With the genetic angle you certainly need to treat aggressively which it sounds like you are already agreed to.
The surgeon may be able to look at the nerve area on the rhs & make the decision for you. i.e if the tissue looks suspicious or not when operating. Obviously the MRI only goes down to see a certain size & that is the usual problem. Just not knowing if there are bad cells which will cause trouble or just die off.
I'm sure you are aware radiotherapy can be used as a salvage/second treatment if the histology proved the capsule breached or psa began to rise after surgery. Certainly removing the primary tumours gives you an advantage. What's gone can't regrow. Others might suggest go for external beam R/T in the hope that nerves would recover in time. But there's always the chance the prostate will not be truly ablated ( as in my case & others here ).
It may well be that you can indicate preference to the surgeon with the proviso that if he feels a wider margin should be done, then he will do so on the day. Either way, your psa will need careful monitoring with follow-up R/T promptly used if required.