Force boot partition size in NT Unattend

I am modifying a Unattend.txt file that we use for our NT4WRK installation. I am trying to figure out how to set the size of the boot partition to be 7.8 gigs. Can I do this? The only parameter I’ve seen is ExtendOemPartition which I have set to 1 for partitions greater than 2gigs. Currently the way I have it setup, the partition size gets created to the default max for a boot partition. Any thoughts?