Since it sounds like yer not cookin the corn, I don't recon there's gonna be a lot of starch in the wash to convert....maybe a percent.
If you decided to cook the grain, I'm sure you'd get a lot
You could always try some sort of simple single infusion mash method that would get you some grain conversion and most of the grain flavor ...
Something like this:
heat your 15 gallons of water up to 155 degrees. turn off heat.
dump all 14 pounds of grain in the water ... stir well n cover boiler with a sleepin bag for 30-60 mins, stir every 10 mins.
then, stir in your 10# sugar until disolved. next ladel out a bowl for breakfast
(it always smells so good).
cool to 70 degrees n pitch the prestige WD yeast (check yer SG too).
ferment til dry (prolly 1 week)