A general fitting guideline is to start adjustments at the feet (foot – pedal interface), work up through lower body joint angles with seat positioning, and then address cockpit set up via reach and drop to the bars, and finish with control lever ergonomics.
But if the rider interview and on-bike assessment indicate the seat contact zone as a cause of problems, doesn’t it make sense to start there first, especially if a new / different saddle is indicated? If height, setback, and angle have all been addressed, and then the saddle is changed out, all that adjustment finessing has to be redone.
Assess the butt –saddle interface.
1. Does the rider complain of any direct contact issues?
2. Are there any indications of a kinetic chain effect from an unsuitable saddle or saddle position? E.g. saddle presents with nose down and rider complain of hand tiredness or numbness (from pushing back to keep from sliding forward).
3. Is the saddle too narrow in relation to the rider’s sit bone width?
4. Does the rider lack stability on the saddle even though the leg extension angles are appropriate?
If the answer to any of the above is “yes”, then it makes sense to address the causative issue first, so as to prevent rework later. However keep in mind that issues that present at the butt-saddle interface can also be due to overreaching to the pedals or the bars. Keep the whole bike-body relationship in mind.