"Your B17 doesn't look "saggy." My B17s were comfortable right away -- after I got them adjusted properly. I found that I had to adjust the front higher than the back or I always felt like I was slipping forward. It looked funny, but otherwise the saddle just wasn't right."
The saddle doesn't look saggy, but when you apply pressure to the top it definitely gives, and quite a bit before I retensioned it the other day. What you can see though is the complete lack of forming to my sit bones. I'm fairly lean and don't have much padding getting in between the saddle and sit bones so I don't think that's an issue.
I have played with saddle angle and fore-aft position and I feel that I've found a pretty good setting. However, the bottom line is that the leather is loose.
I wonder why the tops of some saddles--like Brooks--aren't flat. You need the rear level so you don't slide forward, but that requires the nose to be inclined. The inclined nose just seems to make riding in the drops and hoods less comfortable since you're leaning forward more into the nose. Perhaps the B17 was only intended for fairly upright positions? (I ride a touring bike with saddle and handlebars about even)
"Instead of tensioning the leather, try re-adjusting your saddle tilt. I have thousands of miles on my touring Brooks (I have 6 others), and I have never had to tension the leather screw.
Also, have you used Proofhide on it?"
The saddle's been proofided a few times over the year that I've had it.
So I'll probably try lacing the sides and tensioning as needed to keep the leather taught. When it eventually gives out I might try a Brooks Professional or look into other options. Thanks for the advice so far. I know there are tons of posts about B17s already but I thought the more info out there the better.