If you use a Max PP02 of 1.2, On 32%, the MOD is 90 feet.
At 100ft = 30m = 4.0 ATA, the max % of 02 is 30%. For 82 ft = 25m = 3.5 ATA, the Max % of 02 is 34%. (again, based on MOD @ PPO2 of 1.2)
I hope this helps you to figure out your recreational depth floors. You should be able to do...