I hope you don't mind, but just food for thought'. I sold siding for a contractor in Florida who was very successful with this approach.
After you are comfortable with seeing a profit at the sq/ft figure, find a crew who would independantly install for a set price on the entire job. Thereby moving the risk for labor to the indepentdant and freeing you to bid more jobs.
Of course all this will depend on your own game plan. I just thought it seemed like a great idea.
