When using my spooky generator with the foot plates, I put the amplitude to 20 volts and often I don't feel much the current.

Regarding the amplitude when using foot plates, you can do two things:
The first one is to raise the conductivity of the worst conductive portion of your skin, your soles. This can be done simply with water. Moisten a towel or paper, and put it between your soles and the electrodes.

The second one is to use the boost cable. Please be aware that the boost cable or Spooky boost 2.0, if used with inverse+sync, will raise the amplitude to 40V. This amplitude, with wet feet, and low frequencies, could deliver a VERY VERY unpleasant sensation, or even make your muscles to spasm, so be very careful, and be prepared to stop your rig (or to disconnect one of the foot plates).

If you are using the colloidal silver port, there is 10k resistor connected in the circuit to keep the current down, which will prevent you from unpleasant sensation.

For more details, please check:
http://www.spooky2.com/forums/viewtopic.php?f=6&t=4644