After researching my options, I decided to go with RPGNow for the print copy of Blackmarsh. It will be 8.5 by 11, 16 pages. So the full map will be properly display within. Since I will be using color the maps will (crossing fingers) be a full gray scale. I also setup the PDF sides of things which will be free and working with Brave Halfling to coordinate our releases.
The only downside is that the I have to wait for the print files to be approved from a technical standpoint. A process that takes way longer than Lulu. Then I get to order it and see how it printed and hope that nothing went wrong. Otherwise I get to repeat the whole cycle again.
One thing I did different this time is made sure my files are PDF/X-1a:2001 compliant. This is a standard used by printing houses to ensure that the printed color is really what the color the customer wanted.
Because I did this I am going to set up a b/w versions on lulu and RPGNow to see if it succeeds in avoiding halftoning of my maps. The key element of exporting to a PDF/X-1a:2001 PDF was converting all my images to either a 1 bit b/w format for line art or 32-bit CMYK (not RGB or grayscale) for the images. I hope you find this helpful for your own projects.
We are on track for an April release. And below is the full letter size cover. Click to enlarge.