There was a recent discussion about that here: http://www.homebrewtalk.com/f39/conf...tarter-103468/
It seems to me that Palmer's numbers are off - that the gravity would be too high. In one place in his book, he uses a figure of 42 points per pound per gallon, and in another place 40. Either way, I think if you used a half pound of DME, you would be pretty close to your desired gravity. I have heard some advice that you don't want a high gravity for a starter - see the "Fourteen essential questions about yeast starters" at mrmalty.com.
For my last brew, I made a one quart starter 48 hours in advance with 3 ounces of DME, then used a cup of that for a hydrometer sample (gravity was in low 30's) and pitched the vial of WLP001 to the remaining pint and a half. On Sunday, I pitched the entire starter to my wort (O.G. = 1.051) - fermentation took off within 12 hours, has been blowing krausen up into the blowoff tube on a six gallon B.B. for the last two days, so I'd say it's working great.
I get the impression that it isn't really all that critical.