I'm currently running a Eve probe convoy mission designed to farm science from Eve and Gilly. Two of these probes, creatively named Eve-1 and Eve-2, are designed to use Eve's atmosphere to capture into its SOI. I really don't know the perfect altitude for aerobraking on atmospheric planets, but all I know is that if you go too high, you won't get captured and if you go too low, you will have unplanned lithobraking. Info is advised for all atmospheric bodies. Thanks KSP community for your help! -Crikeycrapper