Frankly Bob I think selling some parts makes the most sense FOR YOU and your ability to have a life.
Unlike sex this is not something you can do all by yourself.
It needs some redundancy in people as well as servers - you can't be expected to handle tech support / advertising / other issues all alone.
I really love the advertiser supported model CFS started with - as someone who grew up in a time and place when you did not "come out" this was one of the first and few gay sites where I posted anything - it was sort of my cyber "coming out" and had I been required to pay a subscription from day one I am sure I would have chickened out.
The free / premium services option seems to work on some of the other websites and now that they have Visa gift cards I would have the courage to use something like that.
One issue CFS has that is a good and bad is an older clientele. The younger generation do everything on their phone - it is only those of us "more mature" guys that still use message boards - but it is also one of the things I have loved about CFS and try to keep going - because those of us that do participate often can have interesting discussions.
I hope you find a model that works - but it needs to work for YOU as well as CFS.