FAA part 25 is readily available in PDF format on the FAA.gov website as is the Advisor Circular AC25-7D (the current issue). I could not find anywhere where the pilots' elevator force is required to overcome full nose down or full nose up trimmable stabilizer force.
The Advisory Circulator did say that with the aircraft stabilizer set at the maximum nose down or nose up position that would not trigger a configuration warning the aircraft should be flyable at the forward and aft CG limits.
The question is then what is the difference between full stabilizer travel and travel required to illuminate the configuration light.