I think the deacal should be 4"x4" min. If you have doubts, print it out to measure 4"x4" and look at it from a distance. It may need to be 5x5, but that might take up too much window space.

I'll be looking into altering the design to make it a white outline logo to be used as a clear window sticker. I think white lines read better than black on window stickers. Any thoughts?

Oh yeah, I'm good for 6.

Mike