Hunter, can you tell us the serial number of the car in question?
As for low-balling, yes, you probably offended the owner of the 2007 F430, and that's why you never heard back. The key to low-balling is to first establish a dialogue with the seller before you insult him with an offer. So your initial inquiry should be about condition, mileage, service history, completeness and correctness in its current condition compared to how it was ordered new, etc.
Is the car listed through a dealer or a private seller?
The answers to these questions will tell you two things: 1. Is the car perfect, and therefore not worth low-balling? 2. How valuable is it compared to the asking price, and therefore just how low can you go ($20K? $50K?)?
You want to find out about all of the little details: does the car have books and tools, the window sticker, service records, a car cover, all keys and fobs, etc.? If anything is missing, that gives you an opportunity to work your angle.
What are the cars options? Is it loaded? Power Daytona seats, carbon fiber interior trim, black top (or a less popular off-color top), shields, carbon fiber rear segment, standard five-spoke wheels or Challenge wheels, colored calipers or black calipers, etc.? Carbon ceramic brakes became standard on all Ferrari models across the board, so that's not a selling point for an '09 - so if the seller is touting the ceramics as part of the reason for the asking price, use this knowledge to knock it down a peg.
But your most important tool is communication. Talk to the seller, ask him pertinent questions about the car before you make an offer. This opens the line of communication and could unintentionally put you in a position of power through knowledge (maybe he confides that he's selling because of a divorce). If the first e-mail he receives from you is an offer way below what he's asking, it's not unreasonable to expect him to completely disregard you. But a seller will be less likely to simply ignore your low-ball offer if you've already exchanged dialogue; at the very least, he'll come back with a number higher than yours but lower than his initial asking price - at which point, the haggling has begun.
Good luck, and keep us posted - and try to let us know the serial number if you can.
I need an Aventador!