bear, it's much easier once you figure out your system. i know, for instance, that i experience a drop of about 6°F on a normal day when i add my grains to my preheated water. This is true for my keg mash tun, but is different in my stockpot and likewise in my cooler.
i try not to regulate too much. once i have it where i want, i let it sit for the mash. then it doesn't matter greatly how much it drops. besides, the higher you fill your stockpot, the less heat loss you will experience. so, the more grain you use the better it works!
i recently used this method with 10 lbs of grain. i think i could do 12 with a thick mash (and a bigger pot for the sparge.) i might give that a shot next week.
Mirage, that will certainly do the trick! there are always variations depending on where you buy it. i've tried that exact recipe with red wheat and white wheat, british chocolate and pale chocolate and american chocolate, belgian munich and german munich, wlp300 and wlp380, etc. it's always a winner
what is the alpha acid content of those hops? that's the only thing that may be off...if they are a bit higher AA%, you may wish to use only 0.75 oz, but it will probably be fine either way.
oh, and you may wish to get an ice pack for your yeast if your shipping will take a few days. those yeasties are as important as the rest of the ingredients.