Would be 1 minute predator spot cool down for each FT player too much? In 15 minutes gameplay with 4 FT members you would be able to spot predator only 60 times.
EDIT:
15 seconds cooldown for whole FT when predator is successfully spotted, like this:
15:00 - game starts
14:30 - anybody try to guess predator position as he moves somewhere, unsuccessfully
14:25 - again same as before
14:20 - you spot predator, FT shoot and predator run his ass away
14:10 - predator returns, can’t be spotted by anybody
14:05 - FT can spot predator again