I have basically overexposed by 1 2/3 stops the film and I am wondering whether there's any way to partially compensate with development.
Hello,
What you did was to under expose, not over expose.
The best thing you can do now, IMO: Shoot a sacrificial test roll (or two) the same way, try different processes on it, and see what you get. Use your experimentation to inform your decisions with the vacation rolls. If the pix are really important, this is well worth it, IMO.
What I would do is start out with a highly dilute reduced agitation development to "fake" a little extra speed in the shadows. Try HC-110 at very high dilution, for instance 1:100 (easily mixed from concentrate) or 1:127 (easily mixed from stock) using a semi stand method. Neither of these will fully develop your film because there will not be enough developer activity (assuming 250 mL of working solution and one roll of 35mm) but don't worry, because it is only the first step, and it has its purposes. This will develop a very flat negative in terms of contrast, but one with a little extra density in the shadows. Then I would dump that developer out and pour in a more normal dilution to boost the contrast a little (not too much, though). I'd probably use the normal dilution that you use, but at half the time you normally use it.
In a way, it is sort of like "pre intensification". It gives you a little more "initial meat" into which your normal dilution can bite.
I only might try such a stupid procedure because of the high contrast of this emulsion. I would probably not bother to do something like this with a less contrasty film.
Then I would take a look at the negs, and if they needed more contrast, I might tone them to get it, or I might see how well I could do with some prints first.