If you call them by name, they usually respond personally. If you receive a form letter, spend a little money and send another certified.

Tell them you have many friends with whom you discuss these matters, and you all agree. Word of mouth is the most effective advertisement strategy.

You kept your text short and to the point. Excellent!

Consider hand writing it. When you appear to take that kind of time, believe you me they notice and take it seriously. Emails and mass generated letters... nope.

Demographically your hand written letter is taken to represent the view of 5000 other constituents who don't write.