rate it at 6400 or higher and develop in rodinal and you'll get BIG grain. the ei1600 + 1:3 perceptol mix wasnt too grainy at all and had a nice sharp look to it - but the development time was l-o-n-g. I must admit, I prefer HP5, but then again, I'm not really a fan of extra-prominent grain.

I'll dig out an old print and scan it tomorrow to show you the perceptol and 1600 combination if you like