1. Don't do it
2. Don't make them that big if you do...
Whenever I walk out to my car, the last thing I wanna see is something stuck under the wiper, and I chuck whatever it is. Means someone was either leaning or put hands all over it... no thanks. Plus it's kinda like begging... Secondly, I think a normal business card would suffice, no need for something 4x6...??