Did you consult an attorney before doing this? I'm curious what the ramifications are. Back in my boutique days, we were stiffed several times, but I never wanted to pull a stunt like this for fear of legal retribution.
Instead, I hired some very good collectors, and had a stipulation in my contract that the customer was required to pay collection fees for invoices over 60 days late.
This resulted in my company getting paid in full all but twice.