If you have a good RO, they'll keep track of how many times the timer has gone past 3:20 and be able to do the math.
Timer equipment restrictions are not the fault of the shooter.
Doesn't matter. Maximum time for any stage is 5 seconds per target and 30 seconds.
SHB Page 24, Scoring, 2nd paragraph.
If it takes them 300 seconds to shoot the stage, the maximum time scored is 150 seconds, on a 10-10-4+ stage.
SHB 2024 Pg 13 Stage Conventions:
"Cowboy port-arms is defined as standing upright with the butt of the long gun at or below the waist of the shooter, the muzzle at or above the shoulder, and the long gun held with both hands."
What else needs explaining?