Hi,
f/22 to 16 to 11 to 8 to 5.6 means four stops over. Rating it at 50 will have different effects for different people. That would add two stops for me, as I tested it at EI 200, but it's only 2/3-stop over for my friend Rafael, who tested it at EI 80. Lets just assume it's a 100 film for you, so that means you are over by five stops.
If you are five stops over, and your method of deciding which exposure to use would have placed your very darkest points in the composition as a pitch black (zone 0), then these areas are now exposed so they will be a middle grey! You wont' be able to get them all that much lower with development, since they were placed as a low midtone, so your shadows are going to be very dense no matter what. You also have created a very low contrast situation by shoving a bunch of tones onto your film's shoulder. Underdevelopment will only exacerbate the low contrast situation, but it is still your best option. No matter what you do with development, they are going to be somewhat tough to print, so get ready for that!
With your 12 minute normal developing time, you have leeway to cut a lot of time while still achieving even development. But first, I would work to find your maximum dilution. Find out the minimum amounts of stock solution needed for your developer. Usually you can easily get by with half as much as the manufacturers recommend. Say they recommend 2 oz. stock for a roll. That means you can use 1 oz. and still develop the roll to completion. However, your particular film is going to suck up developer activity like mad. It got 32x more light than it should have. This makes figuring minimum amounts of stock difficult. I might, in fact, go with 2 oz. of stock., and the rest water in this case. Just a guess, to make sure the development is even.
Assuming you are using roll film and can use a 16 oz. tank, since there would be 2 oz. of stock, you can have a 1:7 dilution. If you have an 8 oz. tank, you can only get a 1:3 dilution. If a 32 oz. tank, you can get a 1:15 dilution. The dilution simply gives you longer development times. For a given frequency of agitation, half as much stock for twice the developing time will develop the film the same amount. Therefore, since you are used to 1:3 at 13 minutes, assume 26 minutes at 1:7, if you agitate the same way as normal. A normal development time this long lets you cut an immense percentage of your development time without risking uneven development from too short a development time.
So, I'd assume you need to cut 20% per stop of pulling. (This is WAY rough figurin' here.) Also, I'd assume you can't pull more than three stops, so 26 minutes x 0.8 x 0.8 x 0.8 is about 13:20. About 13 minutes. So, I'd use the normal time, but at twice the dilution. I might even just go with a flat ten minutes just to see what happens.
No matter what you do, your negs are going to be dense, flat, and grainy. You can make up for the density and flatness to a large degree when you print.
You can also use bleach! Great stuff. I use it often to make printing easier when I have intentionally overexposed and overdeveloped in order to get lots of grain.
A good option is to shoot another unimportant roll the same way, and test it first.
BTW, your name is not a reference to SSN-21, is it?
