>> Upon completion of the project and receipt of full payment, this project is considered a “work for hire” under U.S. Copyright Law

It turns out that software cannot be considered “work for hire” under US law. The reason is subtle. Contrary to what one may think that the term “work for hire” implies, “work for hire” is actually a legal term defined in the US Copyright Act. The Copyright Act uses a very narrow definition for “work for hire” — a definition that includes only 9 specific types of works and under which software does not qualify. If you use the legal term “work for hire” in your contracts, many sophisticated clients will object, because you are incorrectly designating their work as “work for hire”and that could have damaging effects on their ownership rights. The correct alternative for software works is to use copyright assignment and avoid the words “work for hire” altogether.

See articles below for more info:

http://www.metrocorpcounsel.com/articles/9954/work-hire-doctrine-almost-never-works-software-development-contracts

http://masslawblog.com/copyright/the-work-for-hire-trap/

Mske sure to have a clause similar to this to make payment of invoice clear:
Client shall pay Developer all undisputed portions of the correct and complete invoices for services rendered in accordance with this agreement within fourteen (7) days after receipt of the invoice.

This may be more for the customer, and Im sure you already have it:
The parties acknowledge and agree that Consultant is an independent contractor. This Agreement shall not create the relationship of employer and employee, a partnership, joint venture or other relationship between Customer and Developer. Customer shall have no authority to bind, obligate or commit Developer by any promise or representation without the prior written approval of Developer.

This clause is for worst case scenario, aka – hard drive + backup failure:
Force Majeure. Notwithstanding any other provision of this Agreement, no party to the Agreement shall be deemed in default or breach of this Agreement or liable for any loss or damages or for any delay or failure in performance due to a cause beyond its reasonable control. The parties shall promptly resume performance hereunder after the force majeure event has passed.

The other thing to add is a “attorneys fees clause” so if you do have to sue you can collect your attorneys fees as well.