While FX-37 is reputed to be a speed increasing developer, don't expect miracles. I regularly used it for tmax100 in 35mm, using it at 1:3 for a development number on Kodak's developmnet dial of 39. That was around 6.5 minutes, I recall. Usually the time for tmax400 speed film would be about 8', but I do not have the tables at hand to confirm these times.
If the CPA2 is a rotary processor, I would suggest that published times, based on intermittent agitaion be cut 15% for where continuous agitaion is used.
Usually I try to develop about 50% over normal times as a first trial time when I attempt a 1 stop push, which using 400tmax at an EI of 800 would suggest. The contrast of the scene does require consideration in the amount of development time though. A low contrast scene may see a 60% push as a first trial, while a high contrast scene, where I can afford to give up some detial in what are likely deeply shadowed areas may only need a 35% push.
I hope this information can let you think about your own situation, and make an educated starting development time to test against.