Went ahead and did it.
It took a lot longer to get three jarfuls - swirled, let settle and poured into the half-pint jars, then repeated three times.
By the third jar, there wasn't enough good stuff left to bother - a thick-a$$ layer of darker, chunky dead yeast. What I got, though, was nice and creamy white with a layer of watery stout.
I'll make a starter for my next Irish brew, but will probably have a back up smack pack just in case.