Playing devils advocate here but are you sure you want to make a king size quilt? Will they really use it on their bed? Usually a t-shirt quilt is geared toward one person, so a lap/snuggle/over the back of the couch size may make more sense in the long run. Could you somehow make those blocks smaller, not sure as much blank t0shirt space, trim more to the design? Just a thought, unless you are determined to go king.