If I remember correctly, FX19 is a good push developer, as one of the products of phenidone exhaustion has somewhat of a replenishing effect on hydroquinone (or some such something like that...I don't know chemistry and my memory is bad, so...).
If this is true, I would not use it for overexposed film.
I would just develop it using the EI 200 time listed on the package, or if there isn't one there, then an EI 400 time. There is one there for 200 (perhaps in Perceptol) if my bad memory serves me correctly.
It is an ISO 1000 film, and that never changes very much no matter what you rate it at.
You are going to have very flat and very grainy pictures no matter what you do. This film is flat out of the box, and the exposure flattened it even more. Your compensating development will add even more flatness. The overexposure will make it grainy(er). You will be able to print them, but not as easily as a normal neg.
p.s. I just looked up some info. I didn't find anything on a phenidone product having a mild replenishing effect on hydroquinone (must have read that about something else), but I did find out that phenidone is highly active unless used with a restrainer, which is not called for in the FX-19 recipe.
