Simple Design Slap... Breaking Benjamin

[Codyfknrocks]

My band is covering "Simple Design" by "Breaking Benjamin" and their bassist Mark Klepaski uses a slap technique through out the song. I'm wondering what note he "pops" on. Ive looked a various tabs and videos. most say 4th or 5th fret on the G string, yet it doesn't sound right. Right now i have a 5 string tuned C-G-C-F-A. In the video it looks like hes hitting the A open. I'm lost. Anybody out there have any clues?

[Gawd]

It's a C, the octave of the root.

[Codyfknrocks]

I thought that as well but it doesn't sound right. The closest I've come is the open A; as C is just too high.