if the UCA remains the same.....if the bottom of the spindle was moved forward, it would increase caster and decrease front fender clearance. If the bottom was moved rearward it would decrease caster but gain fender clearance.
Exactly, and this was brought up to increase clearance at the fender, so the caster effect would be to make the caster more negative. Leaving the spindle symmetric and finding the actual source of the lost clearance is the better solution.