Most of my bikes have a Conquest or Brooks Pro. The Conquest is essentially a Pro with springs. So, the shape is basically the same.
I can usually get the angle pretty close to right the first time by just looking at it since I have so many on other bikes with the same shape saddles already.
Height, for the rough first attempt, I want to put my heel flat on the pedal with leg straight with one leg, the other leg is holding me upright by putting my foot on something solid. After that, frequent minor fine tuning, about a half cm at a time.
Fore and aft, that is a slower fitting process, I might ride several km between each adjustment. But with Brooks, there is very little adjustment possible, so I do not make many adjustments.
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Interesting that you mention saddle change. I recently bought a Redshift suspension seatpost. Installed that on my light touring bike (titanium frame, not a Thorn) and have always had a Conquest on that bike. I am getting my light touring bike ready for my next planned tour. Roughly a thousand miles in June and early July. Mostly pavement (tarmac) but some gravel towpath.
Yesterday concluded that I cannot get the angle right with that saddle and seatpost combination. Most saddles have rails that are almost exactly horizontal when fitted on a seatpost properly. But the Conquest rails are far from horizontal. The Redshift seatpost does not have enough angle adjustment to get the angle right with that saddle.
I had a Brooks Pro on my road bike, the Pro has nearly horizontal rails which is what I needed on the Redshift seatpost. So, swapped saddles between the two bikes yesterday. Which meant lots of fine tuning for height and fore/aft adjustment on two bikes yesterday afternoon. I am sure that I will do a bit more fine tuning later, but got everything pretty close to right.
This saddle change makes sense, the Conquest with springs is a bit redundant on a suspension seatpost, so moving the sprung saddle to the road bike with no suspension makes sense.