SIT-3 Fan

I am considering purchasing an active crossover for my CW lV's. I've settled on a 2 way tube crossover by Marchand. Initially I'd like to use my SIT-3 on the bottom and I highly modified Bottlehead 2a3 on top. A very knowledgable friend will design the passive part separating the mid from the tweeter. I read the slope numbers on-line once and I remember that they were steeper than Cornwalls previous. But just as older guys do.... I can't remember! Can anyone give me the slope numbers?