David- I'm with Harv- try Microphen straight (or Kodak's Microdol-X- nearly the same) for this sort of push. I have had good luck with Microphen @70 degrees F for 16 to 18 minutes at 3200, 17-20 minutes rated at 6400. If you have rolls from this job that are important, I'd say shoot another in similar light and test it. Try running only the first 3rd of the test roll, and then use the second 3rd for a second test if neccesary.(posted 8177 days ago)I would also suggest you do the dev. as a two step process for times above 15 minutes with any developer. e.g., if your time is 16 minutes, pour in developer, process normal for 8 minutes, them dump the dev. and refill with fresh chem for the remaining 8 minutes. You'll get better negs.
As always, test.