i used a m8 rod for the shaft, there is a enough of space in the pump house so the impeller doesnt have to be perfectly centerd.
the drill i used does 2000 rpm.
If you use a drill with a lower rpm, the pressure wil be lower too
i think most of the cordless drills will fit because you can put the clamp on diverend places.
the switch i made later is not in the beginning of the video and the pictures, but you can see it on the end of the video
you can see the video on youtube here is the link.
have a look at my other things for more pumps and other interesting things