At the top of the movement, the total AR should come to ~25% additional weight. This ~25% is of the lifters 1RM competition max. For example, if a lifter benches 400lbs, the accommodating resistance at the top of their speed work should be no more than 100lbs total at the lockout. This goes for the squat as well.
**However recently we've had great success when squatting with BANDS as our AR with the percentage being ~33%. The ability to handle a greater percentage comes with training maturity and the use of overspeed eccentrics when utilizing box squats as we do.