Threating customers is not IMHO a good buisness practice. Is this the first payment missed? Most companies will give you a friendly reminder that you have missed a payment. I missed a credit card payment once, the company called me 15 days later and made it feel like I was tring to rob them. The balance on the card was $2.50 and I just plain forgot to pay it. After that nasty call I cut them a cheque and cut up the card. In todays market consumers want to deal with friendly companies that truly appreciate thier business. People will tell 20 others thier bad experiences with a company before they tell just one about a good encounter. I agree that you must get paid but keeping the customer must also be first considered.
I am in the same field as you (residential installs), although I have had very few troubles with collecting at the end of the job one thing that I will be using this year is a Certificate of Completion. It will have a final inspection punch list for the customer to put in writing any items they may find unsatisfactory. Once these discrepencies have been remedied they will initial them as corrected and payment can be made happily. Quite honestly we are planning this as more of a sales tool than a collection tool but it can work both ways.