There is the old story about men of integrity who did business with just a handshake. That's fine and dandy, but by contrast, why are there so many silly love songs? I guess the point, as obvious as it is, has not been made quite clear yet. Because language is imperfect, and at times is impressionistic, a well-written contact can help avoid misunderstanding, assumptions, gaps in meaning.
I highly recommend the standard forms used by licensed real estate professionals. Each numbered line represents someone else's painful learning curve and will help the current user avoid the pitfalls of miscommunication. As an attorney, this advice may cost me a lucrative opportunity, but I would rather prevent or resolve a problem that merely stir the pot.
Use the standard forms, they are there for a reason, and if possible, avoid free-handed addendum's.