Push Developing Time Help (APX 400)

[luckycharms]

I just got back from wandering and shooting a roll (a whole roll in one outing! I'm getting better at this film wasting thing) of APX 400 at about 1600 (maybe 1/3 stop less on most of it). I've been meaning to try nighttime street photography in a certain area here for a while, and I'm curious to see the results. Unfortunately, rudimentary Googling reveals that not only is there very little info about two stop pushes of APX 400, but also that it seems to be accepted as not a good idea. Regardless, I intend to press on with my venture, but I could use some advice as to developing times.

I'll be using F76+, and I imagine 1+19 (or maybe even more dilute) would be appropriate. The times I do have for APX 400 in F76+ are as follows:

1+9, ASA 400, 20C = 8 minutes
1+9, ASA 400, 24C = 6 minutes
1+19, ASA 800, 24C = 12 minutes

It seems like this should be purely mathematical: If a one stop underexposure adds six minutes, shouldn't another stop add six more? Or would it double again? Or is it none of these (probably this one)?

Any advice that you could collectively offer is greatly appreciated.

 

[luckycharms]

No one has even a wiiild suggestion? I really need to do this as a means of procrastination. I am not looking forward to updating my resume this afternoon or cleaning the bathroom. I'm tempted to just throw it in at 24C 1+19 for about 21 minutes, which is a 100% arbitrary number.

This is definitely not "baby's first steps" or "priceless wedding shots," so I'm willing to experiment.