The J1772 standard allows the EVSE to be set to maximum charge rate via a pulse width modulation of the 1 kHz contact pilot signal. The minimum setting is 6 amps as specified by the standard, which is different that if the standard was properly implemented.
If you are comfortable with electronics, you could likely alter this setting on your existing Clipper Creek EVSE. If not, something like an Open EVSE or Juicebox that can be set by the user might be a better option. There is a guy on one of the Nissan Leaf forums who builds and sells Open EVSE's for a little over cost, I think his name is Glen.
Chocula