master-keying -- 3-step progression?

[GringoLocksmith]

I'm master-keying a bunch of locks for a small apartment building. Because we're doing it on the cheap, we're using Schlage B60 deadbolts and F-series knobs from Home Depot. (I wanted to get cheaper passage levers and good deadbolts, but it's not my money.)

I'm finding that two-step progression isn't good enough for these locks. There are 12 change keys in the system and it doesn't take too much jiggling for some to open locks that they're not supposed to open. I'm thinking about using 3-step progression, which will decrease the number of potential combinations and necessitate the use of more chambers, which introduces other security concerns.

I know that three-step progression will result in both odd and even cuts in the same column, but it's a small system. I can easily spot and pick out MACS violations and one-cut differences between bottom and master pins. Are there any other reasons for avoiding that solution?

[mdc5150]

You could also do what is referred to as a system 70. 0 depth is 1, 2 depth is 2 , 4 depth is 3, 6 depth is 4, 8 depth is 5. Then use a 2 step progression based on those 5 depths.