Look, I know this is kinda a radical suggestion, but why not try batch sparging to possibly \alleviate those problems? At least to me, it seems so obvious.
Jeff, you raise an ominous specter. Now I'm going to have to do some cross-checking on my refractometer too. As mentioned, this may be more reason to end the runoff earlier.
Extra testing for the next brew.
You did point out a little astringency on my German Pilsner that got a Bronze at the 2011 NHC. It was noticed when I sat down and read the scoring. I have been chasing it for a long time, maybe now I have a clue!
Jeff- do you also fly sparge?
For this beer I was doing a step mash using the direct fired kettle, following the Devil's Backbone recipe from this year's NHC.
Denny, for your personal gratification, I now have a Blue 70qt. coleman extreme for single infusions. More volume for big beers. Someday I might try bumping the temp on that using a grant (5 gallon kettle with a ball valve, pump back in to the mash).
I don't have astringency problems on big beers in the kettle, as the gravity does not get that low.
It had to be something giving the astringency, maybe I have now found it.