Donk,
As the gym I go to (not as regularly as I should!) is small, and I tend to choose to go at times when it is quiet, in no way can I match your observations of guys your own size (soft) or larger. Often the showers are empty, which personally I find great.
For what it's worth my observation is that a flaccid penis which is obviously over 7 ins in length is statistically pretty rare. I don't think I have seen one which was clearly bigger than mine since my school days, and that was on just one occasion well before I reached full size myself.
But I agree with you about the the sense of camaraderie ... the most it has amounted to for me is a brief nod or grunt in both directions.
Just one other comment, as you mentioned an older gent, into which category I now fit all too well. I dare say you will notice in time what I have ... there is a gradual loss of elasticity in the tissues. I certainly hang heavier, longer and bulkier than I did, and after sex I take a lot longer to return to "normal" dimensions than before. After the odd occasion when my erection is swollen above its standard size for one reason or another that is particularly so. And in my case, with the jocks supporting me 16 hours a day, I can't really blame it on gravity.
No doubt you are still far too young and fit for this to be a factor .. but maybe you need to be prepared.