In 2008 I cycled JoGLE, over 900 miles, and experienced no bottom issues. "So what!" I hear you cry. The point is that I didn't know what I was doing, I had no proper cycling gear, and I was riding 80-90 miles a day; but I was riding a Brooks B17.
In 2016 I cycled 250 miles in two days, not on a Brooks, and on Day 2 my posterior suffered. In 2017 I did 200 miles in a day, back on the Brooks - again no issues.
I'm planning a 10-years-on rematch with the End-to-End, but this time going the other way, south to north - LEJoG. The thing is, my cycling has come a long way in those ten years. When I set off from John o'Groats in 2008 I assumed a very upright position on the bike. By the time I got to Land's End I was permanently on the drops as I battled into the prevailing sou'westerlies. Since then my riding position has got steadily lower. The B17 is just the wrong shape for an aggressive posture. So I decided for this trip to go instead for a B17 Imperial Narrow (the one with the cut-out), and butcher it in the traditional fashion.
Here are the steps:
1. Remove the Brooks nameplate from the back of the saddle.
2. Trim back the leather flush with the edge of the cantle, and with nice flowing curves to create two flaps that can be folded under. I did this with a Stanley knife.
3. Remove the bag loops with a hacksaw. Finish the steel with a file, and the leather with fine sandpaper.
4. Soak the flaps in water for 24 hours to soften the leather.
5. Fold the flaps under the saddle and secure with a clamp, then leave to dry.
6. Trim and make holes in the flaps, and tie together with a lace or cable ties. I tried cable ties initially (for strength and durability), but I didn't like the way it looked from side on, so I used one of the laces supplied with the saddle. Tied off with a bow for now, but may revert to a reef knot and trim the excess once I'm sure of the tension needed.
7. Finish the leather off with proofide, olive oil, dubbin, or whatever other concoction you happen to believe in. I used lots of olive oil.
Final weight, for the record, is 505 grams.
In 2016 I cycled 250 miles in two days, not on a Brooks, and on Day 2 my posterior suffered. In 2017 I did 200 miles in a day, back on the Brooks - again no issues.
I'm planning a 10-years-on rematch with the End-to-End, but this time going the other way, south to north - LEJoG. The thing is, my cycling has come a long way in those ten years. When I set off from John o'Groats in 2008 I assumed a very upright position on the bike. By the time I got to Land's End I was permanently on the drops as I battled into the prevailing sou'westerlies. Since then my riding position has got steadily lower. The B17 is just the wrong shape for an aggressive posture. So I decided for this trip to go instead for a B17 Imperial Narrow (the one with the cut-out), and butcher it in the traditional fashion.
Here are the steps:
1. Remove the Brooks nameplate from the back of the saddle.
2. Trim back the leather flush with the edge of the cantle, and with nice flowing curves to create two flaps that can be folded under. I did this with a Stanley knife.
3. Remove the bag loops with a hacksaw. Finish the steel with a file, and the leather with fine sandpaper.
4. Soak the flaps in water for 24 hours to soften the leather.
5. Fold the flaps under the saddle and secure with a clamp, then leave to dry.
6. Trim and make holes in the flaps, and tie together with a lace or cable ties. I tried cable ties initially (for strength and durability), but I didn't like the way it looked from side on, so I used one of the laces supplied with the saddle. Tied off with a bow for now, but may revert to a reef knot and trim the excess once I'm sure of the tension needed.
7. Finish the leather off with proofide, olive oil, dubbin, or whatever other concoction you happen to believe in. I used lots of olive oil.
Final weight, for the record, is 505 grams.
We must have been typing at the same time. 
