Lowrider, preferably butt them up to eachother to save on machining time. I don’t remember the working height offhand, but I know I extended it at least a little bit. Something like 5" or 7", if memory serves, but I’d have to check when I get back.
Yeah, I think longer 1/4" bits is pretty much a must. The overall length of the 1/8" ones is tiiiny.