I don't have map pilot but that strikes me as pretty serious overkill. Start with whatever dpi you want for your final print and work backward from there. For a print that big, I wouldn't bother with much above 150dpi unless you REALLY need to get close and inspect details, and then maybe 300 if you're using an outstanding printer. Even with a lot of overlap you should be in pretty good shape with 2 rows of 5 images. I've never tried anywhere near 100 in photoshop, and imagine it would take a good chunk of RAM and a lot of time do its thing. 10 shouldn't be a problem.
FYI the stitch, I think, is limited to 24bit colorspace so you'll want to rough in the color and exposure before doing that part (in LR this is easy as you can tweak one image to your heart's content an then copy all development settings to the rest)
...also just guessing, but I think a higher altitude will benefit you both for the number of pictures and reduced parallax distortion