As mentioned above, Ronald @ AutoSolutions aimed for a small batch run last time, and depending on how the quality of the batch comes out, he may have extras available for sale.
So in response to the question about maximum number of people, I don't know, and I think neither does Ronald; but you guys should still try to put in an order anyway.
Worst case scenario, he'll refund your payment in full, if there are not enough kits to go around.