@bonanzaman
From my experience it is best to follow your doctors advice. They know you medically and your specific medical history to be able to give you a medical recommendation.

My R/O at UFHPTI suggested I could possibly use a wide seat but was not assuring me it would not irritate my prostate. You just don't know what is going to irritate that glan who has gone throught WWIII. My PA at UFHPTI said from his experience do not ride a bike regardless of seat and citing what I wrote above. I asked my Mayo PCP and he adivsed not to ride bike as just can't determine the downward pressure and if there will be irritation to prostate. What another person can do with riding and not having issues will not be what can happen to you. So I chose to take the safest route and stopped bike riding until R/O gave me the okay.

You mentioned your bike is not made for comfort with springs, suspension system so would be pounding your body and prostate. I have a hybrid bike that has suspension and springs. My road race bikes do not as made for speed. Even after radiation was done 2 years ago on long bike rides (hybrid bike has wide seat) my bottom and body can be quite sore.

I was doing Sprint Triathlons prior to my prostate diagnosis and treatments. I wanted to keep my bike riding training up but knew I needed to priortize my need to do what is best for me specifically and my prostate.

I kept up my swimming and jog/walk and two month after treatments ended was back bike riding without issues.